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

Annotations already declare destructiveHint=true and idempotentHint=true, so the safety profile is partly covered. The description still earns credit by explaining the concrete mechanics behind that destructiveness: an empty string clears a text field, tags replaces the entire list, and blocked=true blocks the caller's calls — side effects an agent could not infer from annotations alone.

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 compact sentences, front-loaded with the WRITE classification, followed by patch semantics and the endpoint. Every clause carries operational information; nothing is redundant with the tool name or 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 17-parameter mutation with no output schema, the description covers the essential update semantics and the destructive side effects. It stops short of noting what the response returns or any authorization requirements, but nothing needed to call it correctly is missing.

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 coverage is 100%, so the baseline is 3, and every parameter is already self-documented. The description adds genuine update semantics the schema does not state: omitted fields remain unchanged and empty strings clear text fields, which is critical for correctly invoking a PATCH-style update across 17 fields.

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?

Opens with an explicit verb+resource ("update the given fields of a contact") plus a WRITE marker, making the mutation intent unmistakable against read siblings like placetel_get_contact and placetel_list_contacts. It also disambiguates from placetel_create_contact by specifying field-level patching of an existing record.

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?

Usage is implied through the patch semantics ("omitted fields stay") and the WRITE prefix, which signals this is for modifying existing contacts rather than creating them. However, there is no explicit statement of when to choose this over placetel_create_contact, nor any prerequisite or exclusion guidance.

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