Change a contact

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

The description goes well beyond the annotations by disclosing merge semantics, preservation of unmodeled properties, ETag-based refusal of concurrent changes, lack of version history, and human confirmation. It slightly overstates preservation because the raw_vcard parameter replaces rather than merges, so it does not quite earn a 5.

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 sentences, each earning its place: core merge behavior, concurrency guard, and irreversibility/confirmation. The most important semantic is front-loaded before secondary details.

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 destructive 23-parameter mutation tool, the description is unusually complete: it covers semantics, concurrency, and consequences. It omits the raw_vcard exception and the confirm_token workaround, but these are documented in the schema, so the description remains largely sufficient.

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?

With only 30% schema description coverage, the description needs to compensate, and it does add one global rule: unspecified fields are left untouched. However, it does not explain individual parameter purposes, the special behavior of raw_vcard, or how confirm_token relates to the confirmation flow; the schema carries most field-level burden.

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 description states a specific verb ('Changes') and a specific resource ('the fields named' on a contact), and the title confirms the contact scope. It clearly differentiates from sibling tools such as create_contact, delete_contact, and get_contact by describing partial-update semantics.

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 intended use—modifying an existing contact's fields—is clear from the title and behavior, but the description gives no explicit when-to-use guidance or comparison with alternatives like create_contact, delete_contact, or raw_vcard replacement. There are no exclusions or conditions such as 'use raw_vcard when replacing the whole card'.

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