ecfr-mcp

get_cfr_structure

Read-only

Retrieve the hierarchical table of contents for a CFR title, chapter, part, or subpart to navigate regulations, returning nested identifiers and headings for structure analysis.

Instructions

Get the hierarchical table of contents for a CFR title or subset.

Returns a nested tree of titles, chapters, parts, subparts, and sections with identifiers, descriptions, and byte sizes.

IMPORTANT: Does NOT support section-level filtering (returns 400). Use part or subpart, then walk the children to find sections.

Common patterns:

chapter='1' for all FAR parts
chapter='2' for all DFARS parts
part='15' for FAR Part 15 structure
subpart='15.3' for just that subpart's sections

part/subpart/chapter/appendix accept int or string.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`date`	No
`part`	No
`chapter`	No
`subpart`	No
`appendix`	No
`subchapter`	No
`title_number`	No

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed5 schema fields changedv1.0.7Aug 20, 2026

addedInput schema / properties / appendix

Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "integer"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "title": "Appendix"
+}

addedInput schema / properties / chapter / anyOf

Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "type": "integer"
+  },
+  {
+    "type": "null"
+  }
+]

addedInput schema / properties / part / anyOf

Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "type": "integer"
+  },
+  {
+    "type": "null"
+  }
+]

addedInput schema / properties / subchapter / anyOf

Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "type": "integer"
+  },
+  {
+    "type": "null"
+  }
+]

addedInput schema / properties / subpart / anyOf

Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "type": "integer"
+  },
+  {
+    "type": "null"
+  }
+]

First observedv0.2.6May 16, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations already establish readOnlyHint and destructiveHint, so the description doesn't need to restate safety. It adds valuable behavioral context: the return format (identifiers, descriptions, byte sizes) and the limitation of section-level filtering. This goes beyond the annotations and helps an agent predict behavior, though it doesn't cover all edge cases like error handling for invalid combinations.

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 well-structured with clear sections: main function, return details, an important warning, common patterns, and type conventions. Every sentence adds value without redundancy, and the critical limitation is front-loaded. The length is justified by the density of actionable information.

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?

The description covers the tool's main purpose, return structure, key limitation, and typical usage patterns. It lacks detail on some parameters (date, subchapter) and error behavior, but the information provided is sufficient for an agent to use the tool correctly in most cases. The output schema also helps, so the description doesn't need to explain return values.

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?

With 0% schema description coverage, the description must explain parameter semantics. It provides examples for chapter, part, and subpart, and notes that part/subpart/chapter/appendix accept int or string. However, it does not explain the date, subchapter, or title_number parameters beyond the default value. The given examples are useful but leave significant gaps for a multi-parameter tool.

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 opens with 'Get the hierarchical table of contents for a CFR title or subset,' which clearly states the verb, resource, and scope. It then specifies the output as a nested tree of titles, chapters, parts, subparts, and sections. This unambiguously differentiates it from sibling tools like get_cfr_content or search_cfr.

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

Usage Guidelines5/5

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

The description provides explicit usage guidance, including an IMPORTANT warning about section-level filtering not being supported (returns 400) and recommending to use part or subpart then walk the children. It also lists common patterns with concrete examples (chapter='1' for FAR, part='15', subpart='15.3'), making it clear when and how to call this tool.

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

Deploy Server