Explain query plan

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the readOnlyHint annotation, the description discloses accepted input types, output JSON structure, and presentation constraints such as 'never mention this tool's name' and 'never paste raw JSON unless explicitly asked.' This adds substantial behavioral context beyond annotations.

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 well-structured: front-loaded purpose, then usage guidance, output structure, and presentation rules. Every section earns its place, and there is no filler or repetition of schema details.

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?

The description fully covers tool behavior: what it accepts, what it returns, how to present results, and formatting rules. With the readOnlyHint annotation and output schema present, this is complete for a read-only analysis tool.

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?

Schema covers all 4 parameters with descriptions (100% coverage), so baseline is 3. However, the description adds the critical constraint that sql must be a SELECT statement and not SHOW/DESCRIBE/EXPLAIN, which is not present in the schema. This adds meaningful parameter semantics.

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 clearly states 'Run EXPLAIN on a SELECT query and return the execution plan.' This is a specific verb+resource statement that distinguishes the tool from siblings (query, describe_table) by focusing on execution plans and explicitly restricting to SELECT statements.

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?

Explicitly states when to use: 'Use this tool when the user asks why a query is slow, whether an index is used, or how MySQL will execute a SELECT.' Also provides exclusions: 'Only SELECT statements are accepted (not SHOW/DESCRIBE/EXPLAIN).' This is clear guidance with context and alternatives.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.