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

Annotations already declare readOnlyHint=false, idempotentHint=false, and destructiveHint=false. The description adds useful context by naming the required API key and the PATCH endpoint, but it does not disclose partial-update semantics, whether omitted fields are cleared, or any side effects of updating a contact.

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?

The description is short and front-loaded, with the API key requirement stated before endpoint details. The first sentence repeats the title and the operationId metadata is of limited use, but overall there is no padding or wasted prose.

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 five-parameter mutation tool with only 20% schema description coverage and no output schema, the description is too thin. It notes authentication but omits the semantics of the mutable body fields and the update behavior, leaving the agent with significant gaps before invocation.

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 only 20%, with just id_or_email documented in the schema. The description maps audience_id and id_or_email to the URL path, but adds no meaning for first_name, last_name, or unsubscribed, and does not explain whether the update is partial or full replacement.

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 first sentence, "Update a contact," largely restates the tool name and title. The endpoint and operationId clarify that it is a PATCH to a specific contact resource, but the description never states which contact fields can be changed or how it differs from siblings such as create_contact, delete_contact, or update_broadcast.

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 description gives an authentication prerequisite (`full_access` API key) but no guidance on when to use this tool versus create_contact, delete_contact, or other update_* siblings. There are no exclusions, alternatives, or usage conditions beyond the key requirement.

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