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

Even though annotations already declare readOnlyHint=true and destructiveHint=false, the description adds meaningful behavioral context: counts are read live, cover only active guests, remove excluded guests, count each guest once, and include plus-ones in party-size totals. It also discloses the conditional behavior around returning the public RSVP link only once the invitation is published, which the annotations do not 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?

The description is front-loaded with the primary use case and then delivers dense, relevant detail in a compact space. Every sentence earns its place: usage criteria, live count semantics, party-size calculation, link behavior, parameter source, and the sibling alternative. There is no redundant filler.

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 tool with one well-documented parameter, a read-only annotation profile, and an output schema, the description is complete. It covers when to use it, how to obtain the event_id, what the counts mean, the edge case around plus-ones, and when the RSVP link appears, leaving no practical gap for an agent invoking the tool.

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%, and the input schema already documents event_id as the Lemonvite event identifier, not a guest invitation_id or RSVP URL. The tool description restates this guidance, adding marginal clarity but no genuinely new parameter semantics beyond what the schema provides, so the high-coverage baseline of 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 names a specific resource (Lemonvite RSVP summary) and the exact queries it answers: how many guests are going, declined, maybe, have not replied, or how many adults and children are coming. It also distinguishes itself from lemonvite_list_guests by stating that this tool returns counts, not per-guest details.

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?

The description explicitly states when to use this tool ('when the user asks how many guests are going...') and names the alternative for a different need ('To see which guest said what, use lemonvite_list_guests instead'). It also tells the agent where to obtain the required event_id, making the routing and prerequisites clear.

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