io.github.daedalus/mcp-cryptography

by daedalus

Overview Schema Source Related Servers Discussions Admin

Python

Remote

fernet_encrypt

Encrypt a plain text string with a Base64-encoded Fernet key, returning Base64-encoded ciphertext.

Instructions

Encrypt data using Fernet symmetric encryption.

Args: key: Base64-encoded Fernet key. data: Plain text string to encrypt.

Returns: Base64-encoded ciphertext.

Example: >>> key = generate_symmetric_key() >>> ciphertext = fernet_encrypt(key, "Hello, World!") >>> len(ciphertext) > 0 True

Tool call template

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": {
      "key": "<key>",
      "data": "<data>"
    },
    "name": "fernet_encrypt"
  }
}

Input Schema

Name	Required	Description	Default
`key`	Yes
`data`	Yes

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.1Jul 30, 2026

TDQS

A4.4/5.0

Behavior4/5

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

With no annotations, the description carries full burden. It specifies encryption operation, input/output formats (Base64-encoded key, plain text, Base64 ciphertext), and includes an example. It does not detail error handling or key validation, but is sufficient for typical use.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is concise with clear sections (Args, Returns, Example). Every sentence adds value, no redundancy, and the core purpose is front-loaded.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Despite lack of schema descriptions and annotations, the description provides all necessary details: input format, output format, and a concrete example. Output schema exists, so return values are covered. Enough for correct tool invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema has 0% coverage for parameter descriptions. The description fully compensates by explaining that 'key' is a Base64-encoded Fernet key and 'data' is plain text to encrypt, adding essential meaning beyond the bare string type.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states 'Encrypt data using Fernet symmetric encryption', specifying the verb, resource, and algorithm. It distinguishes from siblings like RSA and AES encryption by naming Fernet.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage through the example but does not explicitly guide when to choose this tool over alternatives (e.g., AES vs Fernet), nor does it state prerequisites or when not to use it.

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