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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds ordering ('newest first') and, importantly, pagination behavior ('Pass next back as cursor for more'), which annotations cannot convey. It is slightly vague in that the 'next' field is never formally defined anywhere (no output schema), leaving the agent to infer it comes from the response.

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?

Three short sentences, front-loaded with the resource and ordering, then the filter, then pagination. Every sentence carries information; nothing is padding.

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 read-only, five-parameter list tool with no output schema, the description covers purpose, ordering, the key filter, and pagination continuation. The only gap is the undocumented response field name for the cursor, which an agent must discover at call time.

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 80%, so the schema already documents q, limit and cursor. The description reinforces the meaning of 'unused' and explains cursor continuation, but adds nothing for q or type beyond the schema. This is the baseline case where the schema does the heavy lifting.

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 the resource precisely ('Files already in this workspace'), its ordering ('newest first'), and its purpose ('reuse one by its id in media_ids'). It does not explicitly contrast with a sibling, but no sibling tool covers media, so the purpose is unambiguous in context.

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 gives a clear use case: look here before uploading again, and pass the id into media_ids. The 'unused' filter's condition is also stated. There are no explicit exclusions or named alternatives, which keeps it short of a 5.

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