fetch_image

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

With no annotations, the description must disclose behavioral traits, but it only states the basic action. It does not explain what 'fetch' entails (e.g., returns binary data, URL, or metadata), error handling, or any side effects.

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 short (one sentence) and to the point, but it could be more structured—e.g., mentioning return type or typical use cases. It is not overly verbose, but it does not add value beyond a baseline.

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 simple schema (1 param, no output schema), the description is insufficiently complete. It fails to clarify the return format, potential limitations (e.g., size, authentication), or how the image is fetched.

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?

The input schema has 0% description coverage for parameters, yet the description adds no additional meaning beyond what the schema already provides (a 'url' parameter with format 'uri'). No constraints, examples, or format details are given.

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 'Fetch an image by URL' uses a specific verb ('fetch') and resource ('image') along with a clear mechanism ('by URL'). This distinguishes it from sibling tools like 'get_artist' or 'get_release', which are clearly different.

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?

No guidance is provided on when to use this tool versus alternatives. For example, it does not clarify if this is for downloading, proxying, or returning metadata, nor does it mention any prerequisites or exclusions.

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