Encode, decode, or reformat text

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

Annotations already set readOnlyHint and idempotentHint to true, so the description doesn't need to repeat those. However, it adds valuable behavioral context: decoding validates input and reports errors rather than returning garbage, and that the indent parameter is ignored by non-json operations. This goes beyond what annotations provide.

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 sentences, front-loaded with the main purpose and operation list. Every sentence adds essential information: first covers all operations, second covers validation behavior. No redundancy or fluff.

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 moderate complexity (multiple transformation types), the description is fairly complete. No output schema exists, but for a transformation tool the return value is self-evident. Parameters are fully described in schema. The only minor gap is no mention of size limits or performance, which is acceptable for a simple transformation tool.

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% (all three parameters have descriptions). The description adds extra semantics: it clarifies that the indent parameter is ignored by every operation except json-format. This adds value beyond the schema's 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 clearly states it applies reversible text transformations, listing specific operations (base64, base64url, hex, URL encoding/decoding, JSON formatting/minification). It directly distinguishes itself from sibling tools like hash_text (irreversible) or decode_jwt (specific JWT only).

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 lists what the tool does but does not explicitly say when to use it versus alternative tools (e.g., for encoding/decoding this is appropriate, but no direct comparison with siblings or exclusions). Usage context is implied by the operation list, but no when-not or alternative guidance is provided.

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