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

Annotations already provide idempotentHint=true, openWorldHint=true, destructiveHint=false, readOnlyHint=false, but the description adds crucial behavior beyond them: explains 429 quota exhaustion is not a transient failure ('don't backoff-retry'), specifies exact error codes and behaviors (403 peer_is_cloud_user), discloses the side effect of consuming daily quota only for new conversations, and warns the agent not to fabricate opener text. No annotation is contradicted; the description notably exceeds annotation coverage.

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 every section earns its place: login note, idempotency, canonical response fields, quota limits with explicit error handling instructions, and cloud user exception. It's well-structured with section headers (【需要登录】, 【返回】, 【每日开场额度】, 【云用户】). It could be slightly tightened, but the density of operational guidance justifies the length.

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 mutation tool with 2 params, no output schema, and richer annotations, the description fully compensates: it covers return fields (conversation, created, openerSent, opener/openerKind), error semantics (429, 403), quota consumption, and prerequisite workflow. The agent has enough information to call correctly and handle all listed failure modes. The only thing not covered is the exact structure of exits in the 429 response, but the description explicitly says 'follow the exits in the response', which is acceptable.

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 both parameters have schema descriptions (peerUserId as '对方用户 id (cuid)', productId as 'optional product consultation topic'). The description adds meaningful context: for peerUserId it names the prerequisite tools to obtain it (get_creator/search_people), and for productId it clarifies it's used for 'which product the consultation is about'. It doesn't add type/format details beyond the schema, but given full schema coverage, baseline 3, and the added usage context pushes it to 4.

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 ('start a 1-1 private conversation') and resource ('with a user'), and explicitly differentiates from siblings by noting idempotency ('returns existing conversation') and by naming alternatives like send_cooperation_request, set_my_chat_opener, and get_my_chat_opener. An agent can tell this from send_message, get_conversation, and send_cooperation_request without opening their schemas.

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 says when to use and not use: 'cannot start conversation with self', 'first use get_creator/search_people to get peerUserId', and for cloud users 'can only send_cooperation_request'. Also gives clear post-call guidance: if openerSent=true, don't repeat the opener; read opener via get_my_chat_opener and change via set_my_chat_opener. This is the strongest possible usage guidance.

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