read_article_image

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

Annotations cover the safety profile (readOnly/openWorld/non-destructive), and the description adds real behavioral context beyond them: the return is an MCP image block, calls are one-at-a-time, payload caps at 4MiB, and the index bound is deliberately raised past the legacy 100-image limit. That last note preempts a plausible false assumption.

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?

Three short sentences, front-loaded with the action and return type, then constraints. Every sentence carries information; the only minor overhead is the slightly verbose framing of the legacy-limit rationale.

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 output schema, the description correctly states the return type and its size limit, and discloses the index-bound behavior — enough for an agent to invoke it. The unexplained article_id identifier format is the remaining gap.

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 coverage is 0%, so the schema only gives types and a pattern. The description explains the meaning behind image_index's otherwise puzzling maximum of 200000 (4MiB page capacity) but says nothing about article_id being a 64-hex hash, leaving half the parameters unclarified.

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: read a single image from an archived WeChat article, returning a native MCP image block. It implicitly differentiates from live-image siblings (read_wechat_image) via '已存档', but never names an alternative, so no explicit sibling routing.

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 only implied by the 'archived article' framing and the 'one image per call' constraint. There is no when-to-use/when-not guidance and no pointer to download_article_images or read_wechat_image as alternatives for other cases.

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