url_decodeDecode percent-encoded text. Fails on a malformed sequence such as a lone % sign. A plus sign is left as a plus; replace it with a space first if the text came from an HTML form. Runs locally.
| Name | Required | Description | Default |
|---|---|---|---|
| text | Yes | Percent-encoded text. |
Changes observed during successful MCP inspections.
Input schema / properties / input / descriptionPrevious value: -"Percent-encoded string"New value: +"Percent-encoded string to decode, e.g. \"hello%20world\" or \"a%3Db%26c%3Dd\". Pass only the encoded component, not a full URL."Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Beyond the readOnlyHint annotation, the description discloses important behavior: 'Fails on a malformed sequence such as a lone % sign,' plus sign handling semantics, and that it 'Runs locally.' These details materially affect how an agent should expect the tool to behave and interpret results.
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?
Four short sentences, each carrying useful information: the core operation, an edge-case failure, a common input variant, and execution locality. There is no filler, and the essential purpose 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?
With only one required parameter, no output schema, and readOnly annotations, the description covers everything an agent needs to invoke the tool correctly: input format, failure behavior, plus-sign handling, and local execution. No critical gap remains.
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?
The input schema fully describes the 'text' parameter, but the description adds valuable semantics: it clarifies percent-encoded input, the malformed-sequence failure mode, and the plus-sign nuance. This enriches the parameter beyond the schema's bare description.
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 a specific verb and resource: 'Decode percent-encoded text.' This clearly distinguishes the tool from siblings like base64_decode and url_encode. The title matches the described behavior, leaving no ambiguity about what the tool does.
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 concrete usage context, including when to preprocess input: 'A plus sign is left as a plus; replace it with a space first if the text came from an HTML form.' It does not explicitly name sibling alternatives or say when not to use this tool, so it falls just short of a 5.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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