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

Annotations already declare readOnlyHint=true, openWorldHint=true, destructiveHint=false. The description adds real value beyond them: it discloses how a URL is inspected (size/type read via HEAD) and gives a concrete expected output example. It does not cover error/unsupported-platform behavior, so not a full 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?

Purpose is front-loaded in the first sentence, and the example and parameter rule follow logically. Slightly long with the quoted example, but each clause (the HEAD mechanism, the ONE-of rule) earns its place.

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 no output schema, the description compensates by showing the shape of the warning ('won't post to Instagram (max 300 MB)') and covers all three input modes. Complete enough for a 0-required, 4-param read tool.

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 baseline is 3, but the description adds the real semantic constraint: 'Provide ONE of' url, media_id, or size_bytes + mime, i.e. the mutual-exclusion rule and the pairing of size_bytes with mime. This is meaning beyond the flat schema.

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+resource (check media compatibility) tightly scoped to 'platforms CONNECTED to this workspace' and to a pre-upload moment. It is clearly distinguishable from write-oriented siblings like upload_media and from list_media.

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?

Explicitly says when to call it ('when the user gives you a file (URL) ... BEFORE uploading or posting') and what to do with the result ('warn them upfront ... then confirm before uploading'). The workflow placement relative to upload_media is unambiguous.

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