read_wechat_image

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

Annotations already signal readOnly, so the description does not need to restate safety. It adds real behavioral detail beyond annotations: encrypted DAT files will not be decrypted, and the supplied path does not prove conversation ownership. This is valuable context an agent needs before calling the tool.

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 very short, front-loads the core action and return type, and each sentence adds necessary information. There is no repetition of schema fields or annotation facts.

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 simple, single-parameter, read-only tool, the description is mostly complete: it states what is returned and the key limitations around DAT files and session ownership. It could briefly mention expected source_path characteristics, but no output schema exists, so the stated return type is helpful.

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. It does add meaning to source_path by specifying it should be a local WeChat standard image path and not an encrypted DAT path, but it does not describe path formats, allowed extensions, or how paths are resolved.

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 names a specific action ('read'), the resource ('local WeChat standard image'), and the return type ('native MCP image'). It differentiates itself from related tools like read_article_image by restricting to WeChat standard images, though it does not explicitly call out sibling tools by name.

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?

It provides useful context about what input paths are expected ('explicitly selected local WeChat standard image') and gives exclusions ('encrypted DAT is not decrypted; path does not prove session ownership'). However, it does not state when to prefer this tool over alternatives such as read_article_image or when a different tool would be more appropriate.

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