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

Annotations already provide readOnlyHint=true, so the description's safety impact is low. It adds the HTTP GET method and endpoint path, but does not disclose behavior such as 404 handling, return shape, or auth requirements. That is acceptable but not rich for a fetch tool.

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 short sentences, no filler. The core action is front-loaded and the API endpoint reference is useful context that 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?

For a one-parameter read-only fetch tool, the description plus schema fully covers what an agent needs to call it correctly. The endpoint is explicit, and no response details are strictly necessary.

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% and the only parameter 'id' is documented as 'The resource id.' The description merely restates that the contact is fetched by id, adding no extra semantic meaning beyond the schema.

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 uses a specific verb ('Fetch') with a specific resource ('a single contact by id'), which clearly distinguishes it from list_contacts, create_contact, and update_contact. It also names the exact API endpoint.

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 phrase 'a single contact by id' gives clear context: use this when you already know the contact id and need exactly one contact. It does not explicitly mention alternatives or when-not-to-use, so it misses the top score.

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