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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering safety. The description adds useful context: assets are produced by a workflow's asset block, and the tool supports slug-prefix browsing and pagination. It also clarifies a limitation ('you cannot upload a binary the user has not given you'), which adds behavioral transparency beyond the annotations.

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 three sentences, front-loaded with the core purpose and URL retrieval, followed by usage guidance and a fallback. Every sentence earns its place—no redundancy or fluff.

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 an output schema present and annotations covering safety, the description covers the tool's purpose, when to use it, the source of assets, and a clear limitation. There is nothing an agent needs to call it correctly that 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?

The schema provides 100% coverage with descriptions for all five parameters, including pagination and slug-prefix behavior. The description reiterates these concepts but does not add new parameter-specific details beyond what the schema already states. Per the rubric, baseline 3 is appropriate when schema coverage is high.

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 ('List') and resource ('binary assets... published to the media CDN'), and clarifies the scope (tenant, media CDN). It also differentiates from siblings like get_asset by focusing on the plural listing and URL retrieval. The purpose is unambiguous and distinct.

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?

It explicitly says when to use this tool ('use this to see what has already been published and to get an asset's URL to embed in a page') and when not to ('If the image or file you need is not here, send the user to... to upload it'), providing a clear alternative action. This is excellent guidance.

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