Explain a query

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

Discloses that the query is not executed and only analyzed, making it safe. Also specifies that input must be read-only SELECT or WITH, covering security constraints.

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?

Two concise sentences; first tells what it does, second tells when to use it. No unnecessary words.

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?

Covers all essential aspects: output (query plan and cost), parameter constraint, and usage context. With no output schema, the description adequately fills the gap.

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?

Adds value beyond schema by requiring the SQL to be a single read-only SELECT or WITH statement, which is not in the schema description.

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?

Clearly states it returns the query plan and estimated cost, differentiating from run_query which executes. The verb 'Returns' and resource 'query plan' are specific.

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 recommends using it to check if a query is cheap before running it. Lacks explicit when-not-to-use, but the contrast with run_query is implied.

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