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

Goes well beyond the annotations (readOnlyHint=false, openWorldHint=true, destructiveHint=false): it discloses the return value (new participant ID), the side effect of an emailed confirmation when send_confirmation is on, the failure mode that a full slot is refused, the confirmation-before-reach behavior, and the Cotlet API key requirement. This is exactly the extra behavioral context annotations cannot carry.

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?

Purpose is front-loaded in the first sentence and the caveats follow in a logical order. There is mild redundancy — the 'SignUpGenius:' prefix echoes the title and 'Signs a person up for a slot' restates the opening — 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?

With no output schema, the description still covers what comes back (participant ID), the significant side effect (confirmation email), the refusal case, and the auth prerequisite. An agent has everything needed to call this correctly and warn the user about the external reach.

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 all six parameters, making 3 the baseline. The description adds some meaning by tying send_confirmation to the outgoing email, but it adds nothing about email, signup_id, or slot_id sourcing beyond what the schema already states.

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 and resource: 'Sign someone up for a slot as the organizer' and 'returns the new participant ID.' That distinguishes it from read-only siblings like list_participants. It does not explicitly name the near-neighbors (move_participant, remove_participant, add_group_member), so it stops just short of full sibling differentiation.

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?

Provides meaningful operating context (default confirmation per call, consent required before reaching other people), which is genuine when/when-not guidance. However it never routes the agent between alternatives such as adding an existing group member versus signing up a new person, so the selection guidance is implied rather than explicit.

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