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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds the underlying API mapping (GET /v1/contacts/{contact_id}), which is contextual but not behavioral – it says nothing about what happens when the id is missing/not found or what the payload contains. With annotations carrying safety, a 3 is appropriate.

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, front-loaded with the operation before the API detail. Nothing is padded, though the Bird endpoint line is of marginal value to an agent deciding whether to call the tool.

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 simple read-only point lookup with one fully documented parameter, no output schema, and readOnlyHint covering safety, the description is close to sufficient. The only meaningful gap is error/not-found behavior, which is minor for this tool class.

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 single parameter contact_id is fully documented in the schema. The description only restates 'by id' and adds no format, prefix, or validation detail beyond the schema, so the baseline 3 applies.

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?

States a specific verb and resource: 'Fetch a single contact by id.' The word 'single' implicitly distinguishes it from the sibling bird_list_contacts, so an agent can tell it is the point-lookup rather than the list operation. It stops short of explicitly naming the alternative, keeping it at 4 rather than 5.

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?

Usage is implied by 'by id' – the agent infers this is the tool to use when it already has a contact_id. However, there is no explicit when-to-use/when-not guidance and no reference to bird_list_contacts for the case where no id is known, which is the main routing decision here.

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