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

Annotations already declare read-only behavior, and the description adds useful behavioral detail: it returns matching ids plus unit, source, vintage, caveat, and district coverage, and warns that non-existent ids fail. This goes beyond the structured annotations without contradicting them.

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, front-loads the most critical instruction ('Use FIRST, before any other tool'), and includes concrete examples. Every sentence earns its place: when to use, what it returns, and why this step is mandatory.

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?

For a single-parameter lookup tool with no output schema, the description is complete: it explains the entry-point role, the input nature, the returned fields, and the failure mode. An agent has enough context to invoke it correctly without additional documentation.

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 description coverage is 100%, with the query parameter already well-documented as plain words and guidance to prefer two or three words. The description reinforces the subject-based nature of the query but does not add substantial new parameter meaning beyond the schema, so the baseline of 3 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 names a specific verb ('find') and resource ('indicator'), and makes the scope unmistakable: it resolves a subject phrase to indicator ids. It also distinguishes itself from all sibling tools by stating that every other tool needs an id from here, so an agent can confidently choose it as the entry point.

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 gives explicit when-to-use guidance: 'Use FIRST, before any other tool, whenever a question names a subject rather than an indicator id.' It also says ids are not guessable and inventing one fails, which effectively tells the agent not to skip this step and to avoid fabricating ids.

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