io.github.daedalus/mcp-cryptography

by daedalus

Overview Schema Source Related Servers Discussions Admin

Python

Remote

fernet_decrypt

Decrypt Fernet ciphertext using a Base64-encoded key and ciphertext to recover the original plain text.

Instructions

Decrypt Fernet ciphertext.

Args: key: Base64-encoded Fernet key. ciphertext: Base64-encoded ciphertext.

Returns: Decrypted plain text string.

Raises: cryptography.fernet.InvalidToken: If decryption fails.

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>",
      "ciphertext": "<ciphertext>"
    },
    "name": "fernet_decrypt"
  }
}

Input Schema

Name	Required	Description	Default
`key`	Yes
`ciphertext`	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, description covers return type and exception on invalid token. Does not mention side effects, but decryption is inherently non-destructive.

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?

Concise, structured with Args/Returns/Raises sections, no redundant information, every sentence adds value.

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?

Given simple tool with 2 parameters and output schema present, description fully covers usage, return, and error case. No gaps.

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% description coverage, but description clearly explains both parameters are Base64-encoded, adding essential meaning beyond bare type information.

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?

Clearly states 'Decrypt Fernet ciphertext,' specifying verb and resource. Differentiates from fernet_encrypt sibling.

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?

Implicitly suggests use when decryption is needed, but lacks explicit guidance on when not to use or alternatives. Sibling tools provide context but no direct exclusions.

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