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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It only states the core transformation and does not disclose how plus signs are handled, whether UTF-8 decoding is applied, or what happens with malformed percent-sequences.

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?

The description is a single sentence with zero filler and the key operation 'Percent-decode' is front-loaded. It is appropriately concise for a simple utility, though the brevity leaves room for more behavioral detail.

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 one-parameter pure transformation with an output schema present, a short description can almost suffice. However, the lack of annotations, missing percent-decoding edge-case behavior, and absence of sibling-tool routing leave an agent with only partial context for correct invocation.

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 for the parameter's meaning. The phrase 'a string' adds only minimal context that `data` is the percent-encoded input, but it provides no format constraints, examples, or caveats about expected input.

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 uses a specific verb and resource: 'Percent-decode a string.' This clearly distinguishes it from encode tools like url_encode and from other decoders by naming the percent-decoding method explicitly. It does not explicitly differentiate from sibling decoders like html_decode, but the percent-decoding term is specific enough.

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?

There is no guidance about when to use this tool versus alternatives. It does not mention that it is suitable for decoding percent-encoded URL components, nor does it point to url_parse for full URL handling or base64_decode for other encoding schemes.

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