Upload an image to WeChat Official Account

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

The description goes beyond annotations by disclosing that the tool requires confirm=true, returns only safe metadata (filename, size, MIME, media_id, CDN URL), and never publishes content. It also implies the need for a logged-in account. These details provide meaningful behavioral context beyond the readOnlyHint/idempotentHint/destructiveHint annotations, with no contradiction.

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 three sentences with the verb and resource front-loaded. Each sentence earns its place: formats, usage modes, safe response, confirmation requirement, and a non-publication guarantee. No redundant or filler content.

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?

Given the tool's moderate complexity and the presence of annotations and a well-described schema, the description covers all essential aspects: what it uploads, accepted formats, usage modes, the confirm gate, safe return metadata, and the non-publication guarantee. The file path root restriction is in the schema, so no critical information 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 75%, and the description adds additional meaning for key parameters: file_path is clarified as a local image with specific allowed formats, usage is mapped to 'material (cover)' or 'article body image,' and confirm is highlighted as mandatory. The response_format parameter is not mentioned in the description, but the schema already describes its enum values and default, so the overall parameter semantics are well-supported.

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 clearly states the tool uploads a local image file to the logged-in WeChat Official Account, and specifies the image formats (JPEG, PNG, GIF) and the two usage modes (material or article body). This distinguishes it from sibling tools that handle reading, reports, and drafts. It also explicitly notes 'Never publishes,' setting it apart from publication actions.

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 description gives clear context on when to use the tool: for uploading local images as cover or inline article images, and notes the requirement confirm=true. It does not explicitly name alternative tools for other scenarios (e.g., reading or publishing), but the purpose clarity and 'Never publishes' provide strong implicit differentiation.

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