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

Beyond annotations (readOnlyHint=false, destructiveHint=false), the description discloses that the tool downloads, copies into storage, and returns a media ID. It also mentions constraints (https only) and failure modes (share links return HTML, not files). This gives the agent a clear behavioral model.

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 concise and front-loaded, starting with the core action. It uses 7 sentences but each adds value: main function, internal process, output, one-step nature, protocol restriction, failure case, and altText guidance. Slightly long but all content is pertinent and well-structured.

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 tool that downloads external media, the description covers prerequisites (public, https, direct URL), the process (download, copy, return media id), and a common failure scenario. It also clarifies how this differs from sibling upload tools. Without an output schema, the description still conveys what the agent receives (a media id).

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 already covers both parameters (url, altText) with descriptions, so baseline is 3. The description adds extra semantics: explains that the URL must be the direct file path, not a share link, and advises writing altText if an image is visible. This goes beyond the schema's literal descriptions.

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 clearly states the tool's function: attaching an image or video from a public URL by downloading it into storage and providing a media ID for publishing. It uses a specific verb ('Attach') and resource ('media from URL'), and distinguishes itself from sibling upload tools like media_upload_link.

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?

Provides explicit when-to-use guidance: for public web media that can be directly fetched. It gives exclusions ('Google Drive and Dropbox share links do not work') and a rule of thumb ('Use a direct file URL that ends in the file itself'). Also instructs when to add altText, which is practical guidance.

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