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

Annotations already state destructiveHint=false and openWorldHint=true, and the description adds genuinely new behavioral facts: nothing is sent to the guest, the action is reversible by removing the guest, and a Cotlet API key with app access is required. Its one gap is not describing what the call returns (e.g., a guest ID).

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?

The safety disclaimer and reversibility are front-loaded, but the text is padded: "Sends nothing" and "It sends nothing to the guest" say the same thing twice, and "Adds one guest to the guest list" restates the opening sentence.

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 nine-parameter mutation with no output schema, the description covers the important decision-relevant facts: reversibility, no notification side effect, and auth requirements. Only the response shape and any duplicate-guest behavior are left unaddressed.

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 schema already documents all nine parameters. The description's note that same-party guests are grouped and can RSVP for each other largely repeats the schema text for 'party' and adds little new syntax or constraint detail, so the 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?

The description states a specific verb+resource (add a guest to the guest list) and narrows scope to one guest with optional party/plus-ones, which distinguishes it from bulk actions. It does not, however, explicitly contrast itself with nearby siblings such as joy_update_guest or joy_assign_guest_tags.

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?

"It runs without asking" implies the call is safe to make without confirmation, which is useful context. But there is no explicit guidance on when to choose this over joy_update_guest or joy_assign_guest_tags, or on prerequisites beyond the API key note.

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