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

Annotations only say the tool writes (readOnlyHint=false) and is not idempotent, but the description adds far more: login requirement, post-create feed visibility semantics (先过后审, no gray release), error codes with remediation routes (organizer_profile_required / profile_incomplete / no_published_product), dedup semantics (same clientRequestId or title within 5 min returns the existing activity with deduped=true), and the deliberate absence of an agent-side organizer-name write path (SMS-gated subtree). 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?

Long but fully earned for a 23-parameter creation entry point: it is organized into labeled sections (需要登录/何时用/组合链/口径·坑) with numbered pitfalls and bold key terms, and the decision-relevant content (when to call, chain position) is front-loaded. No filler sentences; even the COMPETITION reminder that echoes the schema functions as a trap warning rather than duplication.

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 write tool with no output schema, the description nearly suffices: it covers prerequisites, error handling, dedup, auth, and the post-create workflow. The return contract is only implied via the chain (slug → signupPageUrl, deduped=true) rather than spelled out, and the 'exits 里写了各自怎么补' reference presumes external documentation not present here. Minor gaps against an otherwise comprehensive definition.

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. The description still adds genuine meaning: the baseline four-question set that lands when extraQuestions is omitted (and the warning not to hand-build dozens of fields), the 'all extra questions are optional' rule, the organizerName fallback chain with its SMS-verification constraint, and the 5-minute dedup window for clientRequestId. This exceeds baseline by explaining cross-parameter behavior and rationale the schema does not.

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 concrete trigger ('用户说「帮我发一场分享会 / 建一个报名」时调它') and names the exact resource scope (活动本体 + 报名配置一次写入). It declares itself the '唯一正确入口' for in-site activity creation, explicitly distinguishing it from updates (update_activity) and downstream read/management tools. An agent can pick this tool over the ~130 siblings 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?

Gives the exact user utterances that should trigger the call, plus an explicit exclusion: activity body changes go through update_activity. The 【组合链】 section lays out the entire lifecycle (create → get slug/signupPageUrl → read → reconfigure → review submissions → export), so it is unambiguous where this tool sits versus siblings like list_signup_feed, bulk_review_signup_submissions, or issue_signup_export_link.

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