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

Annotations only cover the safety profile (readOnly, non-destructive, openWorld). The description goes well beyond them: the x402 payment flow (402 → PAYMENT-SIGNATURE → delivery), $0.25 USDC on Base, that the tool call is free and only the returned URL charges, and that output is machine-grade. These are exactly the traits an agent needs before paying.

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?

Dense and front-loaded, with the cost and payment mechanics layered after the capability statement. Slightly redundant by restating the title verbatim as the opening sentence, but 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?

No output schema exists, and the description compensates by explaining the return value and follow-up flow (the x402 URL to GET). Direction, size limit, cost, and alternative are all covered, leaving nothing an agent needs to call it correctly.

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 both params (text, direction with en-sw/sw-en default) are already fully documented. The description restates the 120-word limit but adds no syntax or format detail beyond the schema. Baseline 3 applies when the schema carries the semantics.

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 (English↔Swahili localization), the mechanism (instant machine pass, open translation model, in-process), and a hard constraint (up to 120 words). Explicitly distinguishes itself from the human-reviewed 500-word alternative, so an agent can tell the two apart without opening 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?

Names the intended cases (UI strings, alt text, short product copy needed mid-run) and routes to the alternative for higher-quality needs ('for native-quality human-reviewed copy up to 500 words, buy swahili-localization-500w'). The when/when-not split is explicit and actionable.

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