url_decode

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

With no annotations, the description carries full burden. It states 'Has no side effects. Free.' which addresses safety and cost. It also explains error behavior ('or an error if the input contains an invalid percent-escape sequence'). This fully informs an agent about the tool's behavior.

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 three sentences long, each carrying essential information. It front-loads the action and result, followed by behavior and usage. Every sentence earns its place without redundancy.

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?

Given the tool's simplicity (one parameter, no output schema), the description covers all necessary aspects: purpose, usage, behavior (side effects, cost, error handling). No gaps are apparent.

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 coverage is 100% with a clear description of the 'text' parameter. The tool description adds context ('percent-encoded', 'decodeURIComponent') that enriches the schema description, helping the agent understand the expected input format.

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 clearly states the action ('Decode'), the resource ('percent-encoded URL string'), and the result ('plain text'). It also references the JavaScript function decodeURIComponent, providing precise technical context. This clearly distinguishes it from sibling tools like url_encode.

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 explicitly tells when to use the tool ('Use to recover the original text from a URL-encoded value'). It does not explicitly mention when not to use it or alternative tools, but the sibling context (url_encode) and the clear purpose make usage guidelines sufficient.

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