Decode a Base64-encoded string back into plain text. Returns an error if the input is not valid Base64.
Base64-decode a string. Returns an error if the input is not valid base64.
| Name | Required | Description | Default |
|---|---|---|---|
| data | Yes |
| Name | Required | Description | Default |
|---|---|---|---|
| result | Yes |
Changes observed during successful MCP inspections.
v1.0.4Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the behavioral burden. It usefully discloses the error behavior on invalid base64 input, which is genuine value beyond the schema, but says nothing about output format, whitespace handling, or encoding assumptions.
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 with zero waste; the core action is front-loaded and the caveat follows immediately.
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?
An output schema exists, so return values need not be explained. Combined with the error-behavior note, the description is nearly complete for a single-argument decode utility, though the expected input shape remains slightly underspecified.
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?
There is one parameter with 0% schema description coverage; the name 'data' is generic. The description implies the argument is a base64-encoded string via the stated error condition, which adds some meaning, but no format or edge-case details (padding, whitespace, non-string rejection) are given.
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 and operation ('Base64-decode') on a specific resource ('a string'), which cleanly distinguishes it from the sibling encoding_base64_encode and from the other encoding_* tools. An agent can tell exactly what it does without opening the schema.
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 gives no guidance about when to choose base64 decoding over the sibling decoders (encoding_url_decode, encoding_hex_decode) or what input format is expected. For a small utility this is tolerable, but no context or alternatives are offered.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.