base64_decode

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

The description mentions handling non-ASCII characters correctly, adding behavioral context. However, with no annotations provided, it does not disclose error behavior (e.g., invalid Base64 input) or other side effects, which is a gap for a tool with no annotation coverage.

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 with no wasted words. The first sentence immediately states the action and result, and the second provides additional context about character handling and use case.

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 simple 1-parameter tool with no output schema, the description covers core functionality, input, and output format. It could include error handling, but the description is largely sufficient for typical use.

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 already describes the 'data' parameter fully (100% coverage). The description adds value by clarifying the output is UTF-8 text and highlighting non-ASCII handling, which goes beyond the schema's basic 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 explicitly states 'Decode a Base64 string back to UTF-8 text', which clearly identifies the tool's function and distinguishes it from siblings like base64_encode (reverse) and url_decode (different encoding).

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 says 'Use to recover the original text from a Base64-encoded value', providing a clear use case. However, it does not explicitly mention when not to use it (e.g., for URL decoding) or alternatives, but given the simplicity, it is adequate.

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