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

Annotations already mark this as readOnly, idempotent, and non-destructive, but the description adds valuable behavioral context beyond that: every returned item is actually registrable, ordering is already server-set with a defined priority and should not be re-sorted, kinds are real server-computed counts, submitted=true/false indicates prior signup status, and startAtKnown=false means the start time is a placeholder that should not be read to users. No contradiction with 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 description is long but tightly organized into three labeled sections: when to use, follow-up tool chain, and semantics/pitfalls. Every sentence carries operational value, and the critical constraints are front-loaded and highlighted. No filler or redundancy.

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 return semantics, and it does so well: it covers item meaning (signup-able), ordering, kinds counts, submitted flag, startAtKnown placeholder behavior, and how to chain follow-up tools. It also handles the main sibling ambiguity with list_activities. This is complete for an agent to invoke and use the result correctly.

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 baseline is 3 because parameter meaning is already fully documented. The description adds some related behavioral context (e.g., first-screen kinds are real counts, don't reorder the feed), but it does not meaningfully extend the meanings of kind, limit, cursor, or includeExpired beyond what the schema already states.

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 explicitly states the tool lists signup-able opportunities and gives concrete triggers ('最近有什么能报名的 / 这周截止的有哪些 / 有没有黑客松'). It also differentiates itself from list_activities by calling itself the site's only feed for opportunities that can actually be registered for on-site.

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?

It provides an explicit when-to-use section, contrasts itself against list_activities (broader info feed; external events must be registered via organizer's site), and gives a follow-up tool chain: get_signup_activity(slug), submit_signup(slug), and get_signup_gaps(slugs=[…]). This gives the agent clear routing and next-step guidance.

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