MCP Server for OSCAL

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get_child_element

Retrieve a specific OSCAL child element by UUID or token ID, returning its JSON in raw_json. If the ID is ambiguous, retry with parent_doc_uuid to scope the result.

Instructions

Get one child element by UUID or token ID, with its OSCAL JSON in raw_json. If the result is an ambiguous_element_id error, retry with parent_doc_uuid.

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": {
      "element_id": "<element_id>"
    },
    "name": "get_child_element"
  }
}

Input Schema

Name	Required	Description	Default
`element_id`	Yes	UUID or token ID (e.g. ac-1) of the child element. Token IDs are unique only within one document.
`parent_doc_uuid`	No	UUID of one parent document to scope results to. Omit for all documents.

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedv0.7.1Oct 26, 2026

removedInput schema / properties / element_id / default
```
Removed value: -""
```

addedInput schema / properties / element_id / description

Added value: +"UUID or token ID (e.g. ac-1) of the child element. Token IDs are unique only within one document."

addedInput schema / properties / parent_doc_uuid / description

Added value: +"UUID of one parent document to scope results to. Omit for all documents."

addedInput schema / required
```
Added value: +[
+  "element_id"
+]
```

First observedv0.1.0Sep 30, 2026

TDQS

A3.7/5.0

Behavior3/5

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

With no annotations, the description carries the behavioral burden; it discloses the raw_json return field and the ambiguous_element_id error-retry behavior. It does not explicitly state read-only/non-destructive semantics, permissions, or other operational constraints, leaving clear gaps.

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 definition is two front-loaded sentences with no wasted text: the first states the lookup and return payload, and the second states the key error-recovery action.

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

Completeness4/5

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

For a simple lookup with complete parameter descriptions and an output schema, the description covers the mechanics and ambiguity handling sufficiently. It lacks broader routing context relative to the many sibling query/get tools, but nothing essential to invoking it is missing.

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

Parameters4/5

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

Schema coverage is 100%, so the baseline is 3, but the description adds meaning by tying parent_doc_uuid to recovery from an ambiguous_element_id result. It restates the UUID/token-ID forms for element_id but adds useful error-condition semantics beyond the schema.

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 uses a specific verb and resource: 'Get one child element by UUID or token ID' and identifies the returned OSCAL JSON as raw_json. It is clear on its own, but it does not explicitly distinguish this getter from sibling get_/query_ tools.

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?

It provides a targeted retry rule: on an ambiguous_element_id error, retry with parent_doc_uuid. However, it does not explain when to choose this tool over the many list_/query_/get_ siblings or state prerequisites.

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

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