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

Annotations already cover safety (readOnly, idempotent, non-destructive, open world), so the description's added value is explaining what the call actually yields: CV class strings scoped to a single image. That return-content detail matters because there is no output schema, though it omits what happens with no detections or on auth failure.

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 purpose is front-loaded in the first sentence, and the class-string examples plus the invocation example are efficient. The opening fragment 'Detected objects/signs in an image' is slightly redundant with the sentence that follows it, keeping it just short of ideal.

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 two-parameter read tool with no output schema, the description does the important work of characterizing the return payload (detection class names) and shows a complete call. It does not cover empty-result behavior, but nothing an agent needs in order to invoke it correctly 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 coverage is 100%, so both parameters (image_id and _apiKey) are already documented with format hints in the schema. The description merely repeats them in the example, adding no syntax or validation detail beyond what the schema provides; baseline 3 applies.

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 states a specific verb and resource: it returns Mapillary computer-vision detections for a given image id, and it names the class-string format (e.g. "regulatory--stop--g1"). That clearly separates it from mapillary_image and mapillary_images_near, though it never explicitly names those siblings or how the outputs differ.

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: you need an image id, which presumably comes from mapillary_image or mapillary_images_near, but the description never says so or when to prefer this tool over them. The worked example demonstrates a call but gives no when-to-use or when-not-to-use context.

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