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

Annotations only declare readOnly=true, destructive=false, openWorld=true. The description goes well beyond them: it explains the HEAD-based size/type read, the IMAGE FIT rows returned per channel, and the semantics of fits: false with the crop vs. keep choice. This is substantial behavioral detail an agent cannot get from 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?

Front-loaded with the core purpose, and most sentences earn their place. It is on the long side, and the crop-handling / media_fit instructions lean toward create_post's territory, but the density is high and nothing is pure filler.

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?

There is no output schema, so the description carries the return-value burden, and it does: it describes the size/type acceptance result and the per-channel IMAGE FIT rows including the fits flag. Combined with the read-only annotations, an agent has enough to call it and interpret the response.

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 adds genuine value by clarifying the mutual-exclusion grouping: 'Provide ONE of: a public url (size/type read via HEAD), an existing media_id, or size_bytes + mime.' That constrains invocation mode beyond the individual field 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?

States a specific verb and resource ('Check whether a video/image will be accepted by the platforms CONNECTED to this workspace') and pins the timing ('BEFORE uploading or posting'). This clearly distinguishes it from siblings like upload_media and create_post without needing to open a schema.

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?

Explicit when-to-use: 'Use this when the user gives you a file (URL) so you can warn them upfront.' It also sequences the workflow (check, then confirm before uploading) and routes the follow-up action ('pass the answer as media_fit on create_post'), so the agent knows both when to call it and what to do with the result.

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