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

Annotations already cover read-only, idempotent, and non-destructive behavior, so the bar is lower. The description adds useful behavioral detail about how component mode percent-encodes reserved characters while uri mode leaves structural characters like / ? & intact, giving the agent a clear expectation of the transformation.

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 core guidance is packed into two front-loaded sentences that cover function and mode selection efficiently. The trailing 'Source' line is credible provenance but does little to help an agent select or invoke the tool, so a perfect 5 is not warranted.

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?

With full schema coverage, clear annotations, and an output schema present, the description is complete enough for correct invocation. It resolves the main ambiguity—when to use component vs uri mode—and the remaining defaults and return expectations are already captured in structured fields.

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 the baseline is 3. The description meaningfully enhances the mode enum by clarifying the practical difference between 'component' and 'uri', which the schema only names. It does not need to restate defaults because the schema already provides them.

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 opens with 'Percent-encode or decode text for URLs', a specific verb plus resource that clearly states the tool's function. It then explains the two modes, which helps distinguish it from sibling URL tools like hopi_url_parser and from other encoders such as hopi_base64.

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 mode guidance is explicit: component mode is 'right for a single query value' and whole-URL mode is 'right for a complete address', including which characters are preserved. However, it does not explicitly name alternative sibling tools or state when not to use this tool, so it stops short of a perfect 5.

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