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

Annotations already declare readOnlyHint=true, so the safety profile is covered, and the description reinforces that this is a plain fetch by naming the REST endpoint. It adds nothing about what is returned, whether the call must exist, or error behavior, so with annotations doing most of the work this lands at an acceptable but unremarkable 3.

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 core action and free of filler. The endpoint-reference sentence is mildly redundant but earns its place as a locator for the underlying API.

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-by-id tool with complete schema descriptions, a readOnly annotation, and no output schema, the definition is minimally viable. It leaves the return shape and the meaning of fetch_contact's effect on the response entirely to inference, which is a gap but not a crippling one.

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 both 'id' and 'fetch_contact' documented in the schema itself, so the baseline is 3. The description adds no syntax, format, or semantics beyond what the schema already states.

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 ('Get a single call by id') and even maps it to the REST endpoint, so the operation is unambiguous. It does not distinguish itself from closely related siblings such as aircall_get_call_transcription or aircall_list_calls, but the core purpose is clear.

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?

No guidance on when to use this versus aircall_list_calls, aircall_search_calls, or any of the aircall_get_call_* sub-resource tools in the family. The agent must infer that 'by id' means a known single call, and nothing states prerequisites or exclusions.

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