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

With no annotations, the description carries the full burden and does well: it discloses UTF-8-only input, that decoding is strict base64 (implying rejection of invalid input), the exclusions, the cost (1000 atomic USDC), and the auth requirement. It does not describe error behavior or the exact output shape, but the operational constraints an agent must know before invoking are covered.

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 short sentences, front-loaded with purpose, then exclusions, then commercial terms. No filler and nothing redundant.

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?

For a two-parameter, no-annotation, no-output-schema tool, the description covers purpose, scope boundaries, and the payment gate, which is the non-obvious information. It leaves the return format and failure modes unspecified, but nothing critical for correct invocation is missing.

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 compensate. It clarifies that text is UTF-8 and that decode is strict, which adds real meaning beyond the bare string type, but it never mentions the 3000-character limit or the encode/decode enum values explicitly as parameters.

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 both specific verbs (encode/decode) against a precise resource (UTF-8 text <-> base64) in one sentence. The scope exclusions (JWT inspection, binary files, secret handling) separate it cleanly from siblings like text_sha256, json_csv_convert, and url_normalize.

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-not guidance ('No JWT inspection, binary files, or secret handling') and states the precondition that payment authorization is required before paid execution. It stops short of naming an alternative tool for the excluded cases, so it is clear context rather than full routing.

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