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

Annotations already cover safety (readOnlyHint=true, destructiveHint=false), so the description's main addition is the cost disclosure of 1 credit, which is operationally relevant and not present in structured fields. The mention of receiving processed output plus the original text is somewhat redundant with the existing output schema, but the cost note is genuine added context.

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?

Two short sentences plus a cost tag, front-loaded with the core behavior; nothing extraneous. The only waste is the name repeated immediately after the name prefix ('URL Encoder/Decoder: URL Encoder/Decoder').

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, single-purpose transform with an output schema and full annotation coverage, the description provides everything needed to invoke it correctly. Nothing essential is missing, though a note on how URL vs full-URL encoding is handled would have been a bonus.

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, but the description adds value by enumerating the two action values (encode or decode) that the schema leaves unenumerated — the schema's action field only says 'The action to perform'. That clarification directly reduces the chance of an invalid call.

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 states a specific verb pair and resource: it percent-encodes text or decodes URL components back to plain text. That is unambiguous about what the tool does, though it never distinguishes itself from lookalike siblings such as Base64EncoderDecoder, HTMLEntitiesEncoderDecoder, or PunycodeConverter.

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?

Passing a string with an encode or decode action implies the usage pattern, but there is no explicit when-to-use versus when-not-to-use guidance and no pointer to alternative encoder tools. An agent can infer the workflow correctly, but it must do the inferring.

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