Base64-encode or decode a string.
Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.
{
"id": 1,
"jsonrpc": "2.0",
"method": "tools/call",
"params": {
"arguments": {
"text": "<text>"
},
"name": "base64"
}
}| Name | Required | Description | Default |
|---|---|---|---|
| mode | No | encode (default) or decode | |
| text | Yes | Text to encode, or Base64 to decode |
Changes observed during successful MCP inspections.
Input schema / properties / modeAdded value: +{
+ "description": "encode (default) or decode",
+ "type": "string"
+}Input schema / properties / textAdded value: +{
+ "description": "Text to encode, or Base64 to decode",
+ "type": "string"
+}Input schema / requiredAdded value: +[
+ "text"
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are supplied, so the description carries the full disclosure burden. It says nothing about failure behavior on malformed Base64, padding handling, character encoding, or output format — all of which matter for a decode operation that can fail.
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?
A single short, front-loaded sentence with zero padding. It is arguably over-terse rather than verbose, but nothing in it is wasted.
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 trivial two-parameter utility with full schema coverage and no output schema, this is close to sufficient. The remaining gaps are error behavior on invalid Base64 and differentiation from the `encode_base64` sibling, which the description should cover given how cheap it would be.
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 description coverage is 100%, so both `mode` and `text` are already documented in the schema with the same wording the description uses. The description adds no format details, such as whether decode tolerates whitespace or invalid input, or whether URL-safe alphabets are supported.
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 pair (encode/decode) and resource (a string), which is clear in isolation. However, it never distinguishes itself from the sibling `encode_base64`, nor from the other encoding tools (base32, base85, atbash, rot13), so an agent has no basis for choosing between them.
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?
There is no when-to-use or when-not-to-use guidance. The phrase 'encode or decode' describes capability, not context, and with a near-duplicate sibling `encode_base64` present the omission is material — the agent must guess which tool to pick.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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