Post-Quantum Cryptography MCP Server

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pqc_hybrid_decap

Recover a hybrid shared secret by decapsulating an ML-KEM-768 ciphertext and combining it with an X25519 secret key and ephemeral public key.

Instructions

Recover hybrid shared secret using both secret keys.

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": {
      "x25519_ephemeral_public_key": "<x25519_ephemeral_public_key>",
      "pqc_ciphertext": "<pqc_ciphertext>"
    },
    "name": "pqc_hybrid_decap"
  }
}

Input Schema

Name	Required	Description
`key_store_name`	No	Name of stored hybrid key bundle
`pqc_ciphertext`	Yes	Base64-encoded ML-KEM-768 ciphertext from encap
`pqc_secret_key`	No	Base64-encoded ML-KEM-768 secret key
`classical_secret_key`	No	Base64-encoded raw 32-byte X25519 secret key
`x25519_ephemeral_public_key`	Yes	Base64-encoded raw 32-byte ephemeral public key from encap

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.10.0Nov 4, 2026

TDQS

C2.9/5.0

Behavior2/5

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

No annotations provided, so the description carries full burden. It implies a sensitive operation that consumes secret keys but says nothing about error behavior on MAC/KEM failure, whether keys are consumed or zeroized, or what the recovered secret's form is.

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

Conciseness4/5

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

One short, front-loaded sentence with zero waste. However, terseness here comes at the cost of specification rather than being maximally efficient.

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

Completeness2/5

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

For a 5-parameter cryptographic decapsulation tool with two input modes (key store vs. inline keys), no annotations, and no output schema, the description is far too thin. It should state the input-mode tradeoff and the nature of the returned shared secret.

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

Parameters3/5

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

Schema description coverage is 100%, so baseline is 3. The phrase 'using both secret keys' weakly signals the classical_secret_key/pqc_secret_key pair but adds no meaning about the optional key_store_name path or precedence between the two input modes.

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

Purpose4/5

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

States a specific verb+resource: 'Recover hybrid shared secret' using both secret keys. This distinguishes it from single-algorithm pqc_decapsulate, though it does not distinguish it from pqc_hybrid_open or explain the relationship to pqc_hybrid_encap.

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

Usage Guidelines2/5

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

No when-to-use guidance at all. It doesn't say this is the counterpart of pqc_hybrid_encap, nor when to supply key_store_name versus explicit secret keys, nor how it differs from pqc_hybrid_open.

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