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

Annotations already indicate readOnlyHint and openWorldHint, which fit the description (creating a new output without modifying input). The description adds valuable behavioral context beyond annotations: payment via USDC/USDT on Base, x402, no API key, and a 3-free-calls-per-wallet limit. This helps the agent plan for cost and authentication.

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?

Two sentences with no wasted words. The main operation, input, output, and cost model are all stated efficiently. The essential info is front-loaded.

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?

The tool has 6 parameters, but only 2 are required; the schema covers all. Output schema exists, so return structure is handled. The description covers the core function, payment, and free tier, and specifies the input must be a public URL. It could mention file size limits or supported codecs, but that's minor given the schema and output schema.

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 100%, so all parameters are already described in the schema. The description repeats the two required params (url, target_format) and gives example formats, but adds little that isn't in the schema. With full coverage, the baseline of 3 is appropriate.

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?

The description clearly states the tool converts/transcodes public media files via FFmpeg and returns a public output URL. It names the resource (audio/video/image), the action (convert/transcode), and the result. Among siblings (mostly unrelated checks and lookups), it is unique and instantly recognizable.

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?

The description gives clear context for when to use it (converting a public file) and mentions the payment model and free tier. It does not explicitly contrast with alternatives, but no sibling is closely related, so the usage is effectively unique. The 'public' aspect and format list add practical direction.

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