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

Annotations cover readOnly=false and destructive=false; description adds that this is 'Free', states supported formats (JPEG/PNG/WebP) and size cap (≤20MB), and discloses the returned { r2Key, fileName } contract. Does not explain idempotency behavior or rate limits, but the cost/format/size/return details go well beyond 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 purpose, then input contract, then return value, then cost/format, then batch workflow. Dense but every clause carries information. Slightly long for the surface area but no 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?

No output schema, so the description usefully declares the return shape ({ r2Key, fileName }) and the downstream call (create_character_swap). Covers inputs, constraints, cost, format limits, and the batch pattern. Missing only edge cases like what happens on validation failure or URL fetch errors.

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 67% and two params have descriptions. The description adds meaning: characterId sourced from either list_characters (saved actor) or list_character_library (preset), and imageUrl can be an influencer asset, Studio/SeedDance render, or any public URL. The mutual-exclusion rule (supply ONE) is not captured by the schema's minRequired=0.

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?

Specific verb+resource: 'Turn an image you already have into a Character Swap character input — no byte upload.' Clearly distinguishes from swap_upload (byte upload path) and from create_character_swap (the consumer of this output).

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 states the 'supply ONE of characterId or imageUrl' rule, names the sibling list tools (list_characters, list_character_library, list_influencer_assets) for sourcing inputs, and describes the batch workflow: import N characters then call create_character_swap N times. Strong routing guidance.

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