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

Annotations only declare the safety profile (readOnly=false, destructive=false, openWorld=false, idempotent=false). The description adds real behavioral context: per-kind format and size limits (JPEG/PNG/WebP ≤20MB; MP4/MOV/WebM/MKV ≤2GB) and the two-step upload workflow. It omits URL expiry/validity window and auth requirements, keeping it below 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 front-loaded sentences with zero padding: purpose, constraints, then routing to the alternative. Every clause carries actionable information.

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 sufficiently explains what the caller receives (a presigned PUT URL) and the full workflow. Minor gap: it references r2Keys without clarifying whether they are returned from this call or originate elsewhere, and it omits the URL's lifetime.

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 description coverage is 0%, so the description must carry parameter meaning. It covers kind semantics well (enum values plus per-value format constraints that implicitly bound fileType/fileSize), but never mentions fileName or clarifies that fileName/fileType/fileSize are the actual parameters, leaving partial compensation only.

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 immediately: 'Get a presigned PUT URL for a Character Swap input.' It also names the downstream sibling (create_character_swap) and the routing alternative (swap_import_character), so an agent can distinguish it from sibling upload tools without opening anything.

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 and when-not-to-use guidance: use this for raw byte uploads, but use swap_import_character when the character image already exists on VidGuy or lives at a URL. It also spells out the follow-up step (PUT bytes, then pass r2Keys to create_character_swap).

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