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

Goes well beyond annotations by disclosing that exactly one email is sent from the user's account, that a count is returned, that people without email are skipped but counted, and the confirmation/API-key requirements. Annotations only cover safety hints, so this added operational context is genuinely valuable.

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 purpose and efficiently packed, though there is mild redundancy between 'By default you confirm each call' and 'confirm with the user before each call'. Still compact for the amount of behavior conveyed.

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, but the description states the return is a count and explains skip/count behavior, so an agent knows what to expect. Only minor gaps around failure modes or formatting remain.

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, but the description adds meaning by spelling out the recipients enum semantics ('everyone, those who signed up, or those who have not') and the group prerequisite tied to the not_signed_up option.

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 (email) and resource (people on a sign-up) with explicit scope (everyone, signed_up, not_signed_up). An agent can distinguish this from sibling tools like signupgenius_list_participants or signupgenius_get_signup 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?

Gives clear context: recipient segmentation options and the prerequisite that the sign-up be assigned to a group for not_signed_up to work. It doesn't name alternative siblings or explicitly say when not to use it, so it falls short of a 5.

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