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

Goes well beyond the annotations (which only declare non-read-only, open-world, non-destructive). It discloses the external side effect (guests receive the invitation and RSVP link at once), capacity limits, regional constraints for SMS, the default per-call confirmation with a toggle, the requirement to confirm with the user before each call, and the needed Cotlet API key scope.

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, but the definition wastes space: 'Adds guests the way Add Guests does' is filler, and the 'invitation sent right away on an already-sent event' fact is stated twice in near-identical sentences. Useful content, but not tight.

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 2-parameter mutation with annotations and no output schema, the description covers the important behavior an agent needs: side effects on guests, limits, region rules, confirmation expectations, and auth scope. Return-value details are unnecessary here, leaving only minor gaps.

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 both parameters are already documented, and the description largely restates them ('by email or phone', 'every number needs a name', US/Canada only). Baseline 3 is appropriate since it adds little syntax or format detail beyond the schema.

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+resource ('Add guests by email or phone') and is clearly distinguishable from siblings like evite_list_guests or evite_update_guest_rsvp. However, it leans on a circular phrase ('Adds guests the way Add Guests does') that adds no real clarity.

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 the agent concrete operating context: behavior on an already-sent event (invitation dispatched immediately), plan-based guest caps (750 free / 2,500 Pro), and US/Canada-only text invites. It never names an alternative tool or states a when-not-to-use condition, so routing 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.