base64_decodeDecode a standard Base64 string into UTF-8 text. Use this only when the decoded bytes are expected to be valid UTF-8; this tool is not for arbitrary binary output. Base64 is reversible encoding, not encryption. Costs 1 credit.
| Name | Required | Description | Default |
|---|---|---|---|
| input | Yes | Standard Base64 text to decode, maximum 65,536 characters. |
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
Input schema / properties / input / descriptionAdded value: +"Standard Base64 text to decode, maximum 65,536 characters."Output schema / (root)Previous value: -nullNew value: +{
+ "$schema": "https://json-schema.org/draft/2020-12/schema",
+ "anyOf": [
+ {
+ "additionalProperties": false,
+ "properties": {
+ "creditsRemaining": {
+ "description": "Credits remaining after this successful 1-credit call.",
+ "maximum": 9007199254740991,
+ "minimum": 0,
+ "type": "integer"
+ },
+ "text": {
+ "description": "Decoded UTF-8 text.",
+ "type": "string"
+ }
+ },
+ "required": [
+ "text",
+ "creditsRemaining"
+ ],
+ "type": "object"
+ },
+ {
+ "additionalProperties": false,
+ "properties": {
+ "creditsRemaining": {
+ "anyOf": [
+ {
+ "maximum": 9007199254740991,
+ "minimum": 0,
+ "type": "integer"
+ },
+ {
+ "type": "null"
+ }
+ ],
+ "description": "Known remaining credits, or null when no balance can be reported."
+ },
+ "error": {
+ "description": "Human-readable reason the protected tool call failed.",
+ "type": "string"
+ },
+ "status": {
+ "description": "HTTP-style status code for the failure.",
+ "maximum": 9007199254740991,
+ "minimum": -9007199254740991,
+ "type": "integer"
+ }
+ },
+ "required": [
+ "error",
+ "status",
+ "creditsRemaining"
+ ],
+ "type": "object"
+ }
+ ],
+ "type": "object"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The annotations are unusually noisy here (readOnlyHint=false, destructiveHint=true, idempotentHint=false for what is a pure transformation), and the description supplies genuinely useful context the annotations do not: a 1-credit cost and the clarification that Base64 is reversible encoding rather than encryption. It does not explicitly correct the misleading destructive/readOnly flags, so it adds value but leaves a residual gap.
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?
Three short sentences, front-loaded with the core operation, then the applicability constraint, then the cost. No sentence is redundant and nothing is buried.
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-value explanation is unnecessary, and the description covers the operation, the applicability boundary, and the credit cost. Nothing an agent needs to invoke this correctly is missing.
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% and the single parameter is fully documented in the schema, including the 65,536-character limit, so the baseline is 3. The description adds no syntax, padding, or charset detail beyond what the schema already provides.
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 and resource ('Decode a standard Base64 string into UTF-8 text') and pins the output encoding, which cleanly separates it from base64_encode and the hash/hmac siblings. An agent can identify the operation 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?
It gives an explicit inclusion condition ('use this only when the decoded bytes are expected to be valid UTF-8') and an explicit exclusion ('not for arbitrary binary output'), which is strong when/when-not guidance. It stops short of naming the sibling to use instead when binary output is needed, so it is clear context rather than a full routing rule.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.