Slowest statements server-wide

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

Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds a key behavioral trait: it requires the pg_stat_statements extension and will return instructions to enable it if absent. It also implies the output contains statement text suitable for explain_query. This adds meaningful transparency beyond the 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 three sentences, tightly packed with purpose, prerequisites, and a cross-reference to explain_query. It front-loads the primary action and avoids unnecessary elaboration. Every sentence earns its place.

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 simplicity of the tool (2 params, no output schema), the description covers the essential aspects: what it does, the extension dependency, and a pointer to the next step. It doesn't mention ordering direction (descending) or output limit behavior, but these are reasonably inferred. It is nearly complete for a read-only listing 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?

The schema provides descriptions for only one of two parameters (database) and the limit parameter has constraints but no description. The tool description does not mention parameters at all. With 50% schema coverage, the description should compensate, but it doesn't. The limit parameter is self-explanatory from its name and constraints, so a mid-score is appropriate.

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 the tool identifies the statements costing the most, ranked by total execution time server-wide. It distinguishes from siblings by specifying the resource (statements) and the metric (total execution time), and it contrasts with explain_query which is for plans.

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?

The description provides clear usage context: use to find top expensive statements, and then take the result to explain_query for the plan. It also notes the extension requirement and that the tool will explain how to enable it if missing. However, it doesn't explicitly state when not to use this tool versus other query tools, so it gets a 4 rather than 5.

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