Fetch one image from an archived WeChat article and return it as a native MCP image block for vision-capable AI models. Provide article ID and image index to load one image (up to 4 MiB).
读取已存档公众号文章的一张配图，返回原生MCP image块供支持视觉的模型理解；客户端是否展示取决于客户端。每次一张，最多4MiB。
| Name | Required | Description | Default |
|---|---|---|---|
| article_id | Yes | ||
| image_index | Yes |
Changes observed during successful MCP inspections.
v4.1.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true, so the safety profile is covered. The description adds genuinely new behavioral context: the return is a native MCP image block, visibility depends on the client's vision support, and there is a 4MiB per-image ceiling — all of which the annotations do not convey.
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?
A single tightly packed sentence with the resource and return format front-loaded and constraints (one-at-a-time, size cap) trailing. No filler, though the client-dependency clause is slightly tangential to invocation.
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?
It covers the return type and size limit, which is important given there is no output schema. However, it omits how an agent discovers the valid range/count of images for a given article, leaving a practical gap for a tool that reads one image at a time.
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% and neither parameter is explained: the 64-hex article_id source is unstated, and image_index's 1-based indexing and 1–100 range are left entirely to the schema. '每次一张' hints at index semantics but does not clarify whether indices are contiguous or gapless.
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 (读取) plus resource (已存档公众号文章的一张配图) and the return modality (原生MCP image块). An agent can distinguish it from generic sibling tools like read_wechat_image or download_article_images, though it does not name those siblings explicitly to sharpen the boundary.
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 operational constraints (每次一张, 最多4MiB) that imply how to call it repeatedly for multiple images, but never says when to prefer this over download_article_images or read_wechat_image, nor that an article_id must come from a prior fetch/get_saved_article call.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.