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

Annotations declare destructiveHint=true, so the safety profile is partly covered. The description usefully adds that this is a partial update rather than a full overwrite, but it omits that array fields are replaced wholesale, and the stated PUT endpoint sits oddly against the 'only provided fields' claim.

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 short, front-loaded sentences with no filler. The REST endpoint line is mildly redundant but is still a single compact clause that aids debugging.

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 7-param mutation with no output schema, the description covers the core partial-update contract but leaves gaps: nothing about permissions, reversibility, or the replace-not-merge behavior of the array fields. Adequate but not complete.

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%, so the schema already documents id, names, information, and the labelled email/phone arrays. The description adds no syntax or format 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 ('Update fields on an existing contact'), which clearly separates it from aircall_create_contact. Sibling differentiation is implied by 'existing' but no sibling is named explicitly.

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 partial-update sentence ('Only provided fields are changed') tells the agent how to use it, but there is no explicit when-to-use vs when-not or reference to alternatives like create_contact or get_contact. Usage is implied rather than directed.

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