List past guests

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

Annotations already cover read-only/idempotent/open-world safety, and the description goes further by disclosing data provenance, the returned fields (shared_events, last_shared_event), the empty-new-account case, and that those fields stay 0/null when Partiful omits them. That is meaningful behavioral context beyond the structured hints, though ordering and pagination behavior are left unstated.

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?

Four dense sentences, front-loaded with the purpose before constraints and edge cases; each sentence carries information (scope, filter behavior, downstream use, empty-state caveats). It is packed rather than padded, though the last sentence compresses two separate edge cases into one long clause.

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 compensates by explaining what each result represents and how shared_events/last_shared_event can be zero or null. Combined with annotations and a fully described 4-param schema, an agent has enough to call it correctly; only result ordering/volume expectations are 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 baseline is 3; the description still adds value with the negative constraint that there is no per-event filter and by pointing user_id (an output field) at invite_guests. It largely restates query/not_on_event_id semantics that the schema already carries, which keeps it from a 5.

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?

Opens with a specific purpose statement ('People you can invite: your past guests and mutuals') and then defines the exact resource: the set Partiful shows on an event's Invite screen, past guests of your events plus mutuals, with shared-event counts. That scope is clearly distinct from list_guests or invite_guests, so an agent can distinguish it without opening another schema.

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 concrete operational guidance: use not_on_event_id to exclude people already on an event, 'there is no filter by one past event' closes off a plausible-but-wrong usage, and query matches partial names. It also chains to the next step ('user_id goes to invite_guests'), which is real workflow guidance, though it never explicitly contrasts with the sibling list_guests.

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