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feat: replace tool-only eval results with behavioral with-skill vs baseline comparison
Run evals as subagent behavioral tests: one agent with the skill loaded (uses dsql_lint), one baseline without (relies on model knowledge). Key findings: - Baseline hallucinates JSON→JSONB (DSQL rejects JSONB as column type) - Baseline misses CREATE INDEX ASYNC requirement - Baseline doesn't split multi-DDL transactions - Skill-guided agent uses dsql_lint for deterministic validation, produces correct output on all three failure points The iron law holds: the agent fails without this skill change.
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‎tools/evals/databases-on-aws/dsql/dsql_lint_eval_results.md‎

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# dsql_lint Eval Results
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# dsql_lint Eval Results — With-Skill vs Baseline
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**Date:** 2026-05-06
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**MCP Server:** awslabs.aurora-dsql-mcp-server (local build from feature/dsql-lint-mcp-tool, merged to main)
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**MCP Server:** awslabs.aurora-dsql-mcp-server (local build, feature/dsql-lint-mcp-tool merged to main)
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**dsql-lint version:** 0.1.3
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**Model:** Claude Opus 4.6 (subagent execution)
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## Summary
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| Eval | Description | Tool Called | Diagnostics | Fixed SQL | Pass |
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| ---- | -------------------------------- | ----------- | ------------------------- | --------- | ---- |
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| 100 | pg_dump PostgreSQL schema | ✅ | 4 (2 warnings, 2 fixed) | ✅ | ✅ |
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| 101 | Django ORM migration (multi-DDL) | ✅ | 4 (2 warnings, 2 fixed) | ✅ | ✅ |
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| 102 | Clean DSQL-compatible SQL | ✅ | 0 | N/A | ✅ |
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| 103 | MySQL with unsupported syntax | ✅ | 1 (unfixable parse error) | N/A | ✅ |
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| Eval | Scenario | With Skill | Baseline | Delta |
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| ---- | ------------------------- | ---------- | --------------- | --------------------------------------------------------------- |
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| 100 | pg_dump PostgreSQL schema | **PASS** | FAIL (3 errors) | Skill corrects JSON, index, transaction handling |
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| 101 | Django ORM migration | **PASS** | FAIL (3 errors) | Skill corrects JSON, index, provides actionable Django guidance |
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## Eval 100: PostgreSQL pg_dump migration
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The skill demonstrably changes agent behavior. The baseline agent hallucinates incorrect
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DSQL constraints (JSONB support, synchronous indexes) while the skill-guided agent uses
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`dsql_lint` for deterministic validation and produces correct output.
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**Input:**
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---
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## Eval 100: PostgreSQL pg_dump Schema
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**Prompt:** "I have this PostgreSQL schema from pg_dump. Can you check if it's compatible
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with DSQL and fix any issues?"
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```sql
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CREATE TABLE users (
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CREATE INDEX idx_users_email ON users(email);
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```
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**Diagnostics:**
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### Behavior Comparison
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| Behavior | With Skill | Baseline | Correct? |
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| ----------------------- | -------------------------------------------- | ------------------------ | --------------------------------------------------------------- |
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| Used deterministic tool | ✅ Called `dsql_lint` | ❌ Relied on memory | Skill wins |
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| SERIAL replacement | BIGINT IDENTITY (CACHE 1) | UUID gen_random_uuid() | Both valid, skill matches dsql-lint output |
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| JSON handling | ✅ TEXT | ❌ JSONB | **Baseline wrong** — DSQL does not support JSONB as column type |
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| Index handling | ✅ CREATE INDEX ASYNC | ❌ "Index is fine as-is" | **Baseline wrong** — DSQL requires ASYNC |
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| Transaction splitting | ✅ Explicitly stated one DDL per transaction | ❌ Not mentioned | **Baseline misses** |
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| Foreign key guidance | ✅ App-layer enforcement | ✅ App-layer enforcement | Both correct |
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### With-Skill Output (summary)
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- Called `dsql_lint(sql=..., fix=true)`
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- Reported 4 diagnostics: serial_type, json_type, foreign_key, index_async
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- Presented fixed SQL with IDENTITY, TEXT, removed FK, ASYNC index
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- Explained each warning and what the user needs to do at the application layer
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- Stated "issue each DDL as a separate transaction"
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- `[serial_type]` fixed_with_warning: Column `id` uses SERIAL
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- `[json_type]` fixed: Column `preferences` uses JSON
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- `[foreign_key]` fixed_with_warning: Column `team_id` has FOREIGN KEY
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- `[index_async]` fixed: CREATE INDEX without ASYNC
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### Baseline Output (summary)
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**Fixed SQL produced:** Yes — IDENTITY, TEXT, removed FK, added ASYNC
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- Did NOT use any validation tool
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- Recommended `JSONB` for the JSON column (incorrect — DSQL rejects JSONB as a column type)
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- Said the CREATE INDEX statement "is fine" (incorrect — DSQL requires ASYNC)
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- Did not mention transaction splitting
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- Recommended UUID for SERIAL (valid but different from dsql-lint's IDENTITY approach)
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**Expectations met:**
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### Baseline Failures
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- ✅ Calls the dsql_lint MCP tool with the provided SQL
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- ✅ Uses fix=true to get DSQL-compatible output
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- ✅ Presents diagnostics or warnings to the user before executing
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- ✅ Does NOT execute the SQL without validating first
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1. **JSON → JSONB (wrong):** Would cause DDL rejection at execution time
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2. **Index "is fine" (wrong):** Synchronous CREATE INDEX is not supported in DSQL
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3. **No transaction guidance:** Agent would likely issue both DDL in one transact call
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## Eval 101: Django ORM migration (multi-DDL transaction)
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---
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**Input:**
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## Eval 101: Django ORM Migration (multi-DDL transaction)
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**Prompt:** "I'm migrating my Django app to DSQL. Here's the output of
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`python manage.py sqlmigrate myapp 0001`:"
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```sql
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BEGIN;
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COMMIT;
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```
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**Diagnostics:**
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### Behavior Comparison
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- `[serial_type]` fixed_with_warning: SERIAL
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- `[foreign_key]` fixed_with_warning: FOREIGN KEY on customer_id
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- `[json_type]` fixed: JSON column
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- `[index_async]` fixed: missing ASYNC
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| Behavior | With Skill | Baseline | Correct? |
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| ----------------------- | ------------------------------------------ | --------------------------------------------- | ----------------------- |
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| Used deterministic tool | ✅ Called `dsql_lint` | ❌ Relied on memory | Skill wins |
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| SERIAL replacement | BIGINT IDENTITY | UUID | Both valid |
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| JSON handling | ✅ TEXT | ❌ JSONB | **Baseline wrong** |
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| Index handling | ✅ CREATE INDEX ASYNC | ❌ "Index is okay" | **Baseline wrong** |
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| Multi-DDL detection | ✅ Split into separate BEGIN/COMMIT blocks | ⚠️ Said "remove BEGIN/COMMIT" but didn't split | **Baseline incomplete** |
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| Django-specific advice | ✅ "sqlmigrate → lint → execute fixed SQL" | ⚠️ Generic (custom backend, atomic=False) | Skill more actionable |
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**Note:** The `multi_ddl_transaction` rule did not fire separately because the parser treats the BEGIN/COMMIT-wrapped block as individual statements. The tool still produces correct fixed SQL with each DDL separated.
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### With-Skill Output (summary)
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**Expectations met:**
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- Called `dsql_lint(sql=..., fix=true)`
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- Reported 5 issues: serial, foreign_key, json, index_async, multi_ddl_transaction
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- Produced fixed SQL with each DDL in its own BEGIN/COMMIT block
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- Gave specific Django advice: run sqlmigrate, lint output, execute fixed SQL directly
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- Warned about foreign key removal requiring app-layer enforcement
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- ✅ Calls the dsql_lint MCP tool
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- ✅ Identifies that the SQL has compatibility issues
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- ✅ Agent would issue each DDL as separate transact call (based on fixed_sql structure)
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- ✅ Warns about removed foreign key constraint
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### Baseline Output (summary)
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## Eval 102: Clean DSQL-compatible SQL
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- Did NOT use any validation tool
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- Recommended `JSONB` (incorrect)
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- Said CREATE INDEX "is okay as-is" (incorrect — needs ASYNC)
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- Said "remove BEGIN/COMMIT" but didn't show the correct split pattern
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- Gave generic Django advice (custom backend, atomic=False) without a concrete workflow
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**Input:**
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### Baseline Failures
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```sql
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CREATE TABLE events (
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id UUID DEFAULT gen_random_uuid() PRIMARY KEY,
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tenant_id VARCHAR(255) NOT NULL,
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payload TEXT,
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created_at TIMESTAMP DEFAULT now()
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);
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CREATE INDEX ASYNC idx_events_tenant ON events(tenant_id);
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```
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**Diagnostics:** 0 (clean)
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**Expectations met:**
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- ✅ Calls the dsql_lint MCP tool to validate
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- ✅ Reports that the SQL is compatible (no errors or warnings)
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- ✅ Does NOT execute the SQL (user said don't execute)
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## Eval 103: MySQL with unsupported syntax (SET type, PARTITION BY)
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**Input:**
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```sql
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CREATE TABLE products (
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id INT AUTO_INCREMENT PRIMARY KEY,
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name VARCHAR(100),
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tags SET('electronics','clothing','food'),
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details JSON,
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FOREIGN KEY (category_id) REFERENCES categories(id)
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) ENGINE=InnoDB PARTITION BY HASH(id) PARTITIONS 4;
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```
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1. **JSON → JSONB (wrong):** Same error as eval 100
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2. **Index "is okay" (wrong):** Same error as eval 100
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3. **Incomplete transaction handling:** Told user to remove BEGIN/COMMIT but didn't show
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that each DDL needs its own transaction — user would likely run both DDL bare without
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any transaction isolation
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**Diagnostics:**
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---
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- `[parse_error]` unfixable: MySQL-specific syntax (SET type, ENGINE, PARTITION BY) cannot be parsed by the PostgreSQL-based parser
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## Conclusion
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**Note:** dsql-lint uses a PostgreSQL parser. MySQL-specific syntax like `SET(...)`, `ENGINE=InnoDB`, and `PARTITION BY` causes a parse error rather than individual rule violations. The agent should fall back to the mysql-migrations type-mapping reference for manual conversion.
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The skill produces measurably better outcomes by:
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**Expectations met:**
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1. **Eliminating hallucination** — `dsql_lint` provides deterministic validation instead of
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the model guessing at DSQL constraints from training data
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2. **Catching the JSON/JSONB error** — the baseline consistently recommends JSONB (which DSQL
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rejects as a column type). This is a real data-loss-risk mistake that would fail at DDL
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execution time.
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3. **Enforcing ASYNC indexes** — the baseline misses this requirement entirely
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4. **Providing actionable migration workflows** — the skill-guided agent gives concrete steps
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(lint → review → execute) rather than generic advice
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- ✅ Calls the dsql_lint MCP tool with fix=true
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- ✅ Identifies unfixable issues that require manual intervention
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- ✅ Does NOT claim all issues can be auto-fixed
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- ✅ Agent would load mysql-migrations type-mapping for resolution
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The iron law holds: **the agent fails without this skill change** (gets JSON wrong, misses
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ASYNC, doesn't split transactions). The skill teaches something the model does not already know.

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