Encode a UTF-8 string to Base64. Use when you need to embed binary data, multi-line text, or special characters safely inside JSON fields, HTTP headers, or data URIs.
| Name | Required | Description | Default |
|---|---|---|---|
| input | Yes | Text to encode |
| Name | Required | Description | Default |
|---|---|---|---|
| encoded | No |
Changes observed during successful MCP inspections.
Input schema / examplesAdded value: +[
+ {
+ "input": "héllo 🌍"
+ }
+]Output schema / propertiesAdded value: +{
+ "encoded": {
+ "type": "string"
+ }
+}Output schema / (root)Previous value: -nullNew value: +{
+ "additionalProperties": true,
+ "type": "object"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, non-destructive, and closed-world, so the safety profile needs no repetition. The description adds the useful fact that input is treated as UTF-8 text rather than raw bytes, but says nothing about padding, URL-safe alphabets, or error behavior on invalid input.
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, zero waste: the purpose is front-loaded and the guidance follows. No restatement of the name or filler.
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 one-parameter, idempotent, read-only transform with an output schema, the description covers everything an agent needs to select and invoke it. Only edge-case behavior (padding, URL-safe variant, invalid input) is absent, which is minor here.
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?
With a single parameter at 100% schema coverage, the baseline is 3, and the description earns one point above it by specifying that the string must be UTF-8 and may contain multi-line or special characters — meaningful beyond the schema's terse "Text to encode".
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 leads with a specific verb+resource ("Encode a UTF-8 string to Base64") that unambiguously contrasts with the base64_decode sibling. It stops short of explicitly naming or contrasting a sibling, which is the only thing separating it from a 5.
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 second sentence gives concrete use cases (embedding data in JSON fields, HTTP headers, data URIs) and the input characteristics that motivate them (binary data, multi-line text, special characters). It provides no exclusions or alternatives (e.g., url_encode for URL contexts), so it falls short of a 5.
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.