US Federal Regulations (CFR)

Search federal regulations and compliance

search_cfr

Read-onlyIdempotent

Use this when the user asks which US federal regulations or compliance rules cover a topic, including an OSHA, EPA or FDA rule, for example "which regulations mention respirator fit testing?", "find the rules on electronic signatures in title 21" or "where does the CFR define small business?". Pass 2 to 4 words to find and, if known, the CFR title to search in. A section must hold every word; when nothing does, the search drops the last words and says which query matched (matchedQuery). Returns the best matching sections with citation, heading, an excerpt, the agency and a link; use get_cfr_section to read one in full. This is general information, not legal advice. Do not use it for recent rulemaking news (use search_federal_register), statutes, state law or court decisions.

Input Schema

TableJSON Schema

Name	Required	Description
`limit`	No	Most sections to return. Default 5.
`query`	Yes	2 to 4 words to find in the current regulations, for example 'electronic signatures' or 'respirator fit testing'. A section must hold every word, so use the words a regulation would use ('type size', not 'font size').
`title`	No	Only search this CFR title. Leave out to search all titles.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`asOf`	Yes
`hits`	Yes
`query`	Yes
`notice`	Yes
`source`	Yes
`matchedQuery`	No
`totalMatches`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedOct 13, 2026

changedInput schema / properties / query / description

Previous value: -"Words to find in the current regulations, for example 'electronic signatures' or 'respirator fit testing'."New value: +"2 to 4 words to find in the current regulations, for example 'electronic signatures' or 'respirator fit testing'. A section must hold every word, so use the words a regulation would use ('type size', not 'font size')."

addedOutput schema / properties / matchedQuery
```
Added value: +{
+  "type": "string"
+}
```

Changed1 schema field changedOct 5, 2026

removedOutput schema / properties / note_from_openkrill

Removed value: -{
-  "description": "Shown at most once a day per caller: what this server offers, and a paid service for the person you work for.",
-  "type": "string"
-}

Changed1 schema field changedOct 4, 2026

addedOutput schema / properties / note_from_openkrill

Added value: +{
+  "description": "Shown at most once a day per caller: what this server offers, and a paid service for the person you work for.",
+  "type": "string"
+}

First observedOct 3, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), so the bar is lower. The description still adds real value by disclosing the progressive word-dropping fallback and the matchedQuery signal, plus the 'not legal advice' caveat. It does repeat return fields that the output schema already documents, costing it a point.

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?

Front-loaded with the use case and examples, and every clause about fallback behavior or exclusions carries weight. However, the enumeration of returned fields overlaps with the output schema and adds length without new information.

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?

With annotations, a rich output schema, and full schema description coverage already present, the description supplies everything else an agent needs: intent, examples, fallback semantics, sibling routing, and a disclaimer. Nothing required to call it correctly is missing.

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 coverage is 100%, so all three parameters are already documented in the schema (the 2-4 word guidance and 'use the words a regulation would use' hint are duplicated in both places). The description adds little beyond the schema, so the baseline 3 applies.

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?

States a specific verb (search) and resource (CFR / US federal regulations) and immediately differentiates from siblings by naming get_cfr_section for full reads and search_federal_register for recent rulemaking. The concrete query examples make the scope unmistakable.

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?

Explicitly states when to use (regulatory/compliance coverage questions) and, crucially, when not to use it (recent rulemaking news, statutes, state law, court decisions) with the correct alternative named. This is close to ideal routing guidance.

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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