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

Annotations provide destructiveHint=true, so the safety profile is partly covered. The description adds the API endpoint and the phone-number caveat, but does not disclose the critical mutation semantics for a destructive tool: whether omitted fields are cleared or left untouched, and any auth requirements. Useful additions, meaningful gaps remain.

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 with the edit scope front-loaded, the phone-number exception second, and the endpoint last. Every sentence carries information and nothing is padded.

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?

No output schema exists, so return values are not required, and the schema fully covers the 4 parameters including the nested object. The description covers editability and a routing caveat; only the partial-update behavior of a destructive mutation is left unstated.

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 100%, so name, email, contact_id, and the custom_fields key pattern/value types are already documented in the schema. The description echoes the c-cf-<id> key convention without adding syntax or format detail beyond it, so baseline 3 applies.

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 (edit) and resource (contact) and enumerates the editable fields (name, email, custom fields). It also distinguishes itself from happyfox_create_contact by routing phone-number edits there, so an agent can separate it from its closest sibling without opening a schema.

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?

Explicitly tells the agent when to use a different tool: phone numbers must go through happyfox_create_contact with the phone id. That is a genuine alternative-routing rule, but there is no broader guidance (e.g. partial vs full update, prerequisites, or when to prefer get_contact first).

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