message_media

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

With no annotations, the description must carry the full burden of behavioral disclosure. It conveys a read-only intent ('locate') and the environment variable requirement, but it does not disclose what happens when media is missing, whether permissions are needed, or how the 'allow_derived_write' parameter affects behavior (implying potential writes). The write-capable parameter is a notable omission for transparency.

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 a single concise sentence with no wasted words. It front-loads the core purpose and includes a key prerequisite, making it highly efficient for an agent to parse.

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?

The tool has 4 parameters, no annotation support, and zero schema descriptions, so the description must provide substantial context. It only specifies the core function and a prerequisite, but omits how to choose between local_id and server_id_str, the meaning of 'chat', and behavior around derived writes. Although an output schema exists, the input side and usage context remain severely under-specified.

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 0%, so the description must compensate by explaining parameters. It provides no details about 'chat', 'local_id', 'server_id_str', or 'allow_derived_write'. The parameter titles in the schema are minimal, and the description does not clarify their roles (e.g., how to specify a message vs a chat, or the implications of derived writes). This leaves the agent guessing.

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 the tool's function with a specific verb ('locate') and resource ('existing local message media paths'), which clearly conveys its purpose. However, it does not explicitly differentiate from sibling media tools like extract_message_files or ocr_message_images, so it misses the top score.

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?

The only usage guidance is the prerequisite 'requires WECHAT_MCP_ENABLE_MEDIA=1', which is a condition rather than guidance on when to use this tool versus alternatives. There is no mention of when-not to use it, nor any reference to sibling tools, leaving the agent without clear selection criteria.

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