Upload / replace a LINE rich menu image

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

Annotations already indicate readOnlyHint=false, idempotentHint=true, destructiveHint=false. The description adds context beyond annotations: it details the download-and-upload process, the SSRF guard, the validation of JPEG/PNG and <=1MB, the domain switch, and the return format. This extra info helps an agent understand side effects and requirements, though rate limits or authentication details are omitted.

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 two short sentences plus a one-line example. Every sentence is informative and earned its place. The purpose is front-loaded, and the structure is efficient with no wasted words.

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 is a mutation with no output schema, the description covers key aspects: what it does, constraints (public URL, format, size), what is preserved (richMenuId, tappable areas), and the return values. The example adds practical context. It is mostly complete, though error scenarios are not addressed, but the core is well-covered.

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?

Input schema has 100% description coverage, so each parameter is already documented. The description does not add new semantic meaning beyond what the schema provides; it only reiterates the validation rules for image_url. With full schema coverage, a score of 3 is appropriate as no extra value is contributed by the description.

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 replaces the image on an existing rich menu without recreating it, preserving richMenuId, tappable areas, and per-user links. This specific verb+resource combination distinguishes it from siblings like line_build_rich_menu (which creates a new menu) and line_design_rich_menu_image (which designs images).

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 explicitly advises when to use this tool: to replace an image on an EXISTING rich menu, and implies that if you need to change layout or other aspects, you should use different tools. It also mentions the SSRF guard and domain switch, guiding users on prerequisites (public HTTPS URL, valid format and size). The example further clarifies usage.

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