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

Annotations only cover idempotent/destructive hints; the description adds substantial behavior beyond that: login requirement, when the opener is actually sent, prohibited content classes, explicit error codes (chat_opener_has_contact, content_rejected, chat_opener_too_long) with no-retry guidance, and null/blank restore-default semantics. This is rich disclosure the annotations do not provide.

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?

Front-loaded with bracketed precondition '[需要登录]', followed by purpose, then constraints, then the chain. Despite being dense, every clause carries actionable information (a rule, an error code, or a routing hint) with no filler.

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?

No output schema, yet the description still communicates failure modes via named error codes and the restore-default behavior, plus workflow chaining. Nothing an agent needs to correctly invoke and recover from this tool 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 schema already documents null/empty→default and the 120-char cap, so baseline would be 3. The description adds meaning the schema lacks: content prohibitions (phone/email/QQ/WeChat/URL), the truthfulness constraint ('写真事，勿编对方需求'), and the associated error code for overflow, directly guiding what values are valid.

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?

States a specific verb+resource (设置新会话自动开场语) and immediately disambiguates from a sibling behavior: '非普通私信；只在新建时发送', distinguishing it from send_message/start_conversation. An agent can identify exactly what this tool writes and where it appears.

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 explicit preconditions ('需要登录', '确认后'), when-not guidance ('非普通私信'), and error-driven guidance ('chat_opener_has_contact或content_rejected勿重试'). The combination chain 'get_my_card→set→get_my_chat_opener→start_conversation' further orients the agent to the workflow and alternatives.

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