eCFR

list_agencies

Read-only

List all agencies with their CFR title and chapter references.

Returns agency names, slugs, and which CFR titles/chapters they own.
Useful for finding which chapter corresponds to an agency's FAR supplement.

summary_only (default True) strips the `children` and most of
`cfr_references` to keep the response compact (~20 KB vs ~100 KB).
References owned by child agencies are merged into the parent row, so
chapter lookups like DFARS (chapter 2, on a DoD child agency) still work
in summary mode. Set False for the full raw payload including children.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "list_agencies"
  }
}

Input Schema

Name	Required	Description	Default
`summary_only`	No

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 21, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Annotations already establish read-only safety and open-world behavior, and the description adds substantial behavioral detail: summary mode strips children and most CFR references, keeps response size around 20 KB versus 100 KB, and merges child-agency references into the parent row. This goes well beyond what the annotations provide and directly helps an agent predict response behavior.

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 front-loaded with the core purpose, then explains the non-obvious summary_only behavior. Every sentence adds useful information; there is no repetition or filler.

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 a single optional parameter, existing output schema, and annotations, the description is complete. It explains the tool's output shape, the practical effect of the summary flag, and a non-obvious child-reference merging behavior, so an agent can call it correctly without additional context.

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 description coverage is 0% and the only parameter has no description in the schema, so the tool description carries the full burden. It explains the default value, what is stripped when True, the approximate response-size impact, how child references are merged, and what False returns, which is complete parameter guidance.

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 uses a specific verb/resource ('List all agencies') and clarifies the returned domain objects: agency names, slugs, CFR titles, and chapters. It also distinguishes the tool's purpose by explaining it is useful for mapping agencies to FAR supplement chapters, which differentiates it from siblings like search_cfr or get_cfr_structure.

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

Usage Guidelines4/5

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

It gives a clear usage context ('Useful for finding which chapter corresponds to an agency's FAR supplement') but does not explicitly state when to avoid this tool or name alternative sibling tools. The guidance is clear enough for selection, but lacks explicit alternatives or exclusions.

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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