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

Adds substantial behavior beyond the annotations: guests without email are skipped and counted in the response, email is free while text requires Messaging Plus, confirmation defaults on and can be toggled, the tool reaches other people, and a Cotlet API key with app access is required. This is exactly the extra context annotations cannot convey.

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 core action and default targeting, and every sentence adds an operational fact. Minor redundancy appears where the no-response default is stated twice and 'Sends the Joy RSVP reminder' echoes the title.

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 send-message mutation with no output schema, the description covers targeting, skip/count behavior, cost tiers, confirmation flow, external reach, and auth requirements. An agent has enough to call it correctly and warn the user appropriately.

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 message, subject, delivery, event_id, and guest_ids. The description restates the guest_ids default rather than adding syntax or format detail, so the baseline of 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 (sends) and resource (Joy RSVP reminder) and clarifies scope: by default to every guest who has not responded. This distinguishes it from siblings like joy_send_email_message and joy_send_thank_you_note, which are different message types.

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?

Explains the default targeting (guests with no response when guest_ids is omitted) and delivery constraints alongside the confirmation requirement. It gives clear context but does not explicitly name an alternative sibling tool to route between.

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