send_private_msg

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

No annotations exist, so the description carries the burden. It usefully discloses that the message body supports text and CQ codes and what auto_escape does, but it says nothing about failure modes (e.g. non-friend targets), rate limits, or what is returned. Partial behavioral coverage only.

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?

Purpose and the upstream action name are front-loaded in the first sentence, and the CQ-code support is called out early. The subsequent ':param' lines largely duplicate the schema descriptions, which is mild redundancy but not verbosity.

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 annotations and no output schema, the description should say more: it never explains that a successful call returns a message_id, nor any error/permission behavior for a mutation-style tool. Core calling information is present, but important operational context 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 description coverage is 100%, so the schema already documents user_id, message and auto_escape; the docstring lines restate them nearly verbatim. The only added value is the concrete CQ-code example format, which is minor. 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?

States a specific verb and resource ('向指定好友或用户发送私聊消息') and names the upstream OneBot 11 action, so the agent can tell it apart from send_group_msg by the '私聊' scope. It does not explicitly name the sibling to prefer/reject, so it falls just short of a 5.

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?

Usage is implied by '私聊' (private vs group) and by the required user_id, but there is no explicit when-to-use/when-not guidance and no mention of prerequisites such as being friends with the target. Adequate but leaves the agent to infer routing between this and send_group_msg/send_msg.

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