Update contact

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

Annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds that it returns the updated contact (valuable, since there is no output schema) and implies a partial patch. It omits what happens to fields not supplied and any auth/rate-limit context.

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 verb and resource, with no filler. The final sentence about the return value earns its place because there is no output schema.

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 23-parameter mutation tool with 9% schema coverage and no output schema, the description is thin: it never hints at the breadth of updatable fields or their formats. An agent must fall back almost entirely on raw schema inspection to call this correctly.

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 9%: just 'id' and 'response_format' are documented, leaving 21 contact fields (fax, tags, blocked, social URLs, etc.) with no meaning beyond their names. The description compensates only marginally by stating that the fields to change are supplied by the caller.

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 an existing contact by id') and clarifies it is a field-level modification of an existing record, which distinguishes it from create_contact and get_contact in the sibling list. It stops short of naming those siblings 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?

'Provide the fields to change' implicitly communicates partial-update semantics and that the record must already exist, which is useful context. However, there is no explicit when-to-use guidance, no exclusion against create_contact/upsert patterns, and no statement about erroring on unknown ids.

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