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

Adds substantial behavior the annotations cannot convey: the outreach-policy check that refuses legal/privacy/system mailboxes, the fact that a found contact is replaced, that enrolled sites retain their enrolled address, and that 'nothing is sent'. This is rich context beyond the idempotent/destructive hints, though error behavior on a refused address is not described.

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?

Front-loaded with the action and kept to three sentences, with the key constraint (nothing is sent) last. The opening sentence is long and colon-heavy, but no sentence is wasted.

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 non-destructive mutation with full annotation coverage and no output schema, the description covers validation, replacement, and side-effect behavior adequately. The only gap is the confirm parameter's role, which the schema already explains.

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 the schema already documents site_id, email, and confirm thoroughly. The description adds no parameter-level detail (it never mentions the confirm guard) and only loosely references the policy check, 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 (enter/set) and resource (a site's contact email), and clarifies it is a manual entry analogous to the Websites drawer. An agent can distinguish this write path from the sibling find_website_contact / reveal_contact read paths without opening any 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?

Describes the usage context clearly — hand-entering an address that gets validated and saved as a 'manual contact, replacing a found one' — which implicitly positions it against contact-discovery tools. It stops short of naming an alternative explicitly or stating when *not* to use it.

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