Run a read-only MySQL query to inspect data or schema. Accepts SELECT, SHOW, DESCRIBE, EXPLAIN, and WITH statements while preventing writes.
Use this when you need to run one read-only MySQL query. It accepts SELECT, SHOW, DESCRIBE, EXPLAIN, and WITH statements only.
| Name | Required | Description | Default |
|---|---|---|---|
| sql | Yes |
| Name | Required | Description | Default |
|---|---|---|---|
| result | Yes |
Changes observed during successful MCP inspections.
v0.2.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate readOnlyHint=true and destructiveHint=false, and the description confirms by specifying only read-only statements. It adds the SQL length limit (12000 chars) and the constraint that only one query is executed, which are behavioral details not in annotations. No contradiction found.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, concise sentence that front-loads the primary purpose (run a read-only query) and lists the accepted statement types at the end. Every word is necessary and there is no fluff.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's simplicity (one parameter) and the presence of an output schema, the description covers the essential aspects: what the tool does, the accepted statement types, and the read-only constraint. It lacks explicit mention of how to use the output or edge cases, but those are likely in the output schema.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The schema has only one parameter (sql) with no description, so schema coverage is 0%. The description does not explain what the parameter should contain beyond 'SQL query', but the tool name and statement types imply it. This is a minimal but acceptable level of compensation; a stronger description would specify the exact format or examples.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description states a clear purpose: run one read-only MySQL query, listing accepted statement types. It distinguishes from siblings by focusing on arbitrary SQL execution versus listing tables or describing a specific table, though it doesn't explicitly compare to them.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
It clearly indicates when to use this tool (when needing a read-only query) and specifies accepted statement types, providing implicit guidance on when not to use it (e.g., for DDL or DML). However, it doesn't explicitly mention alternatives like list_tables or describe_table for simpler needs.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.