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

Annotations only declare destructiveHint=true, so the description carries real weight and does add value with the 'only fields you pass are changed (v3.1 partial update)' clarification, which is genuine behavioral context. However, it does not disclose what happens to untouched fields' risk profile, permission/auth needs, or how the destructive nature manifests (e.g., overwriting existing values), leaving meaningful gaps.

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 sentences, front-loaded with the core action and the partial-update rule. The trailing API-path sentence ('Insightly: PUT /Contacts with CONTACT_ID') is somewhat redundant implementation detail, keeping it just short of a 5.

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 19-parameter mutation with no output schema and only a destructive annotation, the description covers the key mutation semantics (partial update) but omits auth/permission expectations, destructive-behavior detail, and confirmation of which fields are required (deferred entirely to the schema). Adequate but with clear gaps.

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 74%, so the schema already documents most of the 19 parameters. The description's partial-update statement implicitly clarifies that omitted parameters are left unchanged, which is useful, but it adds no syntax or format detail for individual parameters 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?

States a specific verb+resource ('Update a contact') and adds the partial-update semantics plus the underlying API call (PUT /Contacts with CONTACT_ID), making the operation unambiguous. It does not explicitly distinguish itself from the create_contact sibling, but the update verb does most of that work.

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?

There is no explicit when-to-use guidance or comparison to siblings like insightly_create_contact or insightly_update_lead. The partial-update note implies the tool targets existing records, but nothing tells the agent when this is preferable to an alternative, nor are prerequisites (e.g., a valid contact_id) called out.

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