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

Beyond the annotations (readOnly=false, destructive=false), it discloses the 15 MB decoded size cap, the return contract (fileId, mediaUrl, published:false), the fact that upload alone does not publish or incur a posting charge, and that account access is required. This is rich behavioral context the annotations alone do not carry.

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 action and constraints, and nearly every sentence carries distinct information (scope, size cap, return values, next step). It is dense but not padded; slightly long, though no sentence is wasted.

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 and 0% param coverage, the description still covers the action, input constraints, required auth, return values and the follow-on publish step. An agent has everything needed to invoke it correctly and chain it into picorn_posts_schedule.

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 0%, so the description must compensate; it clarifies that mediaBase64 must be raw bytes (not a URL) with a 15 MB decoded limit, and that contentType accepts MP4/WebM/MOV, matching the enum. The caption parameter is left undocumented, so it falls short of full compensation.

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 ('Upload an existing MP4, WebM or MOV clip') and immediately scopes it against the neighboring capabilities by excluding generation, editing and rendering. An agent can distinguish this from picorn_generate_image or the editor tools without opening the 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?

Gives explicit when-to-use guidance ('Download a licensed source clip in your client first; a webpage URL is not video bytes'), the exclusion set (no generation/editing/rendering), and the named next-step alternative picorn_posts_schedule with the exact parameters needed. Nothing about routing is left to inference.

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