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

Annotations already declare readOnlyHint=true, so safety is covered by structured data. The description adds genuinely non-obvious behavior: it can return multiple persons, each carries person_id and person_url, and `none` is a meaningful signal (publisher number or ungrouped registrations) rather than an error. It stops short of describing error/rate-limit behavior, but the not-found semantics are the important detail here.

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?

Three tight sentences, front-loaded with the trigger condition, then return shape, then the not-found case. Every clause carries information; nothing restates the title or the schema.

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?

With no output schema, the description supplies the return shape (person(s) with person_id and person_url), the null-result semantics, and cross-tool routing. For a single-parameter lookup tool with a readOnly annotation, nothing needed to call it correctly is missing.

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 coverage is 100%, so the baseline is 3, but the description adds format guidance the schema lacks: 'up to 11 digits, often written without its leading zeros'. That directly informs how an agent should normalize the value before calling, which the generic schema description 'One IPI name number' does not.

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?

Names a specific verb and resource ('find a songwriter by IPI name number') and explicitly scopes the input to an IPI name number. It also distinguishes itself from the sibling get_songwriter, so an agent can choose between them without opening either schema.

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?

'Use when the user has an IPI name number ... and wants to know which songwriter holds it' gives an explicit trigger condition. It goes further by naming the alternative ('use get_songwriter for one person's details') and by explaining the `none` outcome, so both the happy path and the fallback routing are covered.

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