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

Goes well beyond the annotations by disclosing the cost model ($0.01/call, first 25 free, failed calls free) and explaining why repeated calls are not free, which accounts for idempotentHint=false. 'Reads or computes only and changes nothing' largely restates readOnlyHint/destructiveHint=false, so part of the text is redundant with structured data.

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?

Core purpose and the plus rule are front-loaded, and the example is placed before the commercial details. The pricing sentence is dense and slightly promotional, but each clause (free tier, failed calls free, repeats charged) carries real decision-relevant information.

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-output-schema decode utility this covers purpose, the tricky parameter case, an input example, and cost/safety behavior. The only minor gap is that the return shape (plain decoded string) is left implicit, which is acceptable given the tool's simplicity.

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%, so the baseline is 3; the description still adds value by naming the form-encoding semantics of plus=true and giving a concrete example (text=a%20b%26c) that shows how reserved characters are escaped. It does not add anything about the accepted type flexibility (string/number/boolean) for plus.

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 a specific verb+resource ('Decode percent-encoded text') and clarifies the form-encoding variant. It is distinguishable from url_encode/url_parse by implication rather than by naming them, so it falls short of the explicit sibling differentiation a 5 requires.

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?

'Use to read encoded links and form data' gives clear usage context for when this tool applies. It stops short of naming the inverse tool (url_encode) or stating when not to use it, so no exclusions are provided.

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