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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description goes further by disclosing that draft/unconfirmed rows are returned, that only confirmed=true rows surface publicly, and that a non-empty userId identifies an internal user who can be messaged directly. That is genuine return-semantics context beyond the annotations.

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 bracketed sections (login/role, chain, rules/pitfalls) front-load the essential constraints and each sentence carries content. It is dense but well-organized rather than padded.

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 carries the burden of explaining what is returned — guestId, confirmed status, and userId meaning — and does so. Combined with the chain guidance and access requirement, nothing needed to invoke or interpret the call is missing.

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% and the single activityRef parameter is already documented as a slug or id. The description adds no syntax or format detail beyond the schema, 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 and resource — listing an activity's guest lineup — and adds the scope nuance that unconfirmed draft rows are included. It also marks the access context (login + organizer role), letting an agent distinguish it from guest-collection or candidate tools without opening the 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?

Explicitly names the chained alternatives: use this tool to obtain a guestId, then create_guest_invite_link to mint a self-service card, and use add_activity_guest first for people not yet in the lineup. This gives clear when-to-use and when-to-use-something-else guidance.

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