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

Adds substantial behavior beyond the annotations: a concrete rate limit ('at most a couple per sender per day'), an operational instruction ('Do not retry on error'), and a privacy/data-handling disclosure (message forwarded, not stored; hashed counters retained one day). Annotations only declare it non-read-only, open-world, non-idempotent and non-destructive; the description supplies the practical constraints an agent actually needs.

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?

Four tight sentences, each carrying distinct load: action, consent gate, rate limit/no-retry, privacy. The core action is front-loaded and nothing is redundant with the 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 write tool with no output schema, the description covers consent, rate limiting, retry policy and data handling, which is nearly everything an agent needs. The only gap is that it does not hint at what a successful or failed call returns, which matters slightly given there is no output schema to fall back on.

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 83%, so the schema already documents params like from_name, message and reason (with its enum). The description adds no syntax or format guidance for any parameter, so baseline 3 is appropriate.

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 ('Send'), a named recipient ('Patrick Vieira'), the medium ('by email'), and the acting relationship ('on behalf of a person'). This is instantly separable from the read-only siblings (get_profile, list_faq, list_skills, list_work), which all retrieve information rather than send anything.

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?

Gives an explicit precondition: 'Only use this when the person has asked you to contact him and has approved the message,' which functions as a when-to-use gate and an implicit when-not (no consent). It does not name an alternative route, but none exists among the siblings, so the guidance is effectively complete context without a formal fallback.

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