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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds the return payload (capture time, coordinates, heading, camera type, sequence id, thumbnail size) which is genuinely useful with no output schema, but it says nothing about error behavior for a bad/expired id or a missing token.

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?

Two tight sentences with the purpose and return set front-loaded, followed by one example. The example largely duplicates the schema's own 'examples' block, which is mild waste, but nothing else is padded.

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 2-parameter, fully annotated, read-only lookup with 100% schema coverage, the description covers purpose and enumerates the return fields — which matters because there is no output schema. Only the not-found/error path is left unexplained.

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 100% and both parameters are documented in-schema, including the API-key format. The description's inline example restates the same shapes but adds no new semantics, so 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 names a specific verb+resource pair ('Details for a Mapillary image. Given an image id, returns...') and the 'given an image id' framing implicitly separates it from the geo/location-based siblings mapillary_images_near and mapillary_detections. It stops short of naming those siblings, so an agent must infer the routing rather than read it.

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: the tool is the one to call when you already hold an image id, versus the search sibling when you don't. There is no explicit 'use this instead of X when Y' statement and no statement of prerequisites or failure conditions.

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