Post-Quantum Cryptography MCP Server

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pqc_decapsulate

Decapsulate a KEM ciphertext with a supplied or stored secret key to recover the shared secret for post-quantum key establishment.

Instructions

Decapsulate a shared secret using a KEM secret key

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": {
      "algorithm": "<algorithm>",
      "ciphertext": "<ciphertext>"
    },
    "name": "pqc_decapsulate"
  }
}

Input Schema

Name	Required	Description
`algorithm`	Yes	KEM algorithm name
`ciphertext`	Yes	Base64-encoded ciphertext from encapsulation
`secret_key`	No	Base64-encoded secret key
`key_store_name`	No	Name of stored KEM keypair

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 are provided, so the description carries the full behavioral burden and delivers almost none. It does not state that decapsulation is deterministic, what happens on an invalid ciphertext or wrong key (implicit rejection vs error), whether key material is logged, or what the response contains.

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?

A single front-loaded sentence with no filler, which is the right shape for this tool. Its brevity tips into under-specification rather than being genuinely tight, but nothing is redundant.

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 security-sensitive KEM operation with no annotations and no output schema, the definition should explain the key-source semantics, failure behavior, and return value. None of that is present, leaving an agent unable to call it confidently with only two of four parameters required.

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 every parameter is already documented, and the description adds no format or constraint details beyond naming the secret key. The critical relationship between secret_key and key_store_name (presumably mutually exclusive or one required) is unaddressed in both places.

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?

The description names a specific cryptographic operation (decapsulate) and its output (a shared secret) plus the key material it consumes, which is far more precise than the tool name alone. It does not explicitly distinguish itself from the sibling pqc_hybrid_decap or pqc_encapsulate, so an agent must infer that this is the non-hybrid counterpart.

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?

There is no guidance on when to call this versus pqc_hybrid_decap, nor on choosing between the two optional key sources (secret_key vs key_store_name). The one decision an agent must make—which of the two optional parameters to supply—is left entirely unexplained.

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