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

Annotations already declare readOnlyHint=false, openWorldHint=true, and destructiveHint=false, but the description adds real value beyond them: the accepted file types, the constraint that the link must be public http(s), the return value (media id), and the credit-cost behavior. It omits file size limits, duplicate handling, and whether the download is synchronous, which keeps it from a 5.

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 tight sentences: capability and formats first, return value second, cost behavior last. Nothing is repeated from structured fields and no sentence 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 one-parameter import tool with no output schema, the description covers inputs, accepted formats, the returned id, and the credit implication. Minor gaps remain around size limits, error behavior for unreachable or private URLs, and any post-import processing delay.

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 the baseline is 3, but the description meaningfully constrains the single url parameter by naming the supported formats and requiring a public http(s) link, which is more than the schema's terse 'Public link to the file'.

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?

States a specific verb (download/import) plus resource (media) and enumerates accepted formats (JPEG, PNG, WebP, GIF, MP4, MOV), which cleanly separates it from sibling generators like make_video, make_carousel, and create_post.

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?

Clearly signals the workflow context by saying the returned media id is passed to create_post, and the credit note implies this is the path for existing assets rather than generated ones. It stops short of explicit exclusions (e.g., when to prefer make_video_from_my_videos or list_media), so not a 5.

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