An MCP server that parses and validates NACHA/ACH files, exposing two file-analysis tools.
parse_nacha_file — Parses a NACHA file into full structured JSON: file header, batches (header, entries with addenda, control), and file control.
summarize_nacha_file — Returns a condensed summary: batch count, total entries, total debit/credit amounts, SEC codes present, and validation issues.
Both validate record structure and cross-check entry hash, debit/credit totals, and entry/addenda counts, reporting mismatches as issues.
Supports IAT batches and addenda type codes 10-18.
Both tools take a single input: an absolute file_path to the file on disk.
Runs over stdio using the MCP protocol, connectable from Claude Code, GitHub Copilot (VS Code), Claude Desktop, and other MCP clients.
Click on "Deploy Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type @ followed by the MCP server name and your instructions, e.g., "@nacha-mcp Parse /path/to/payments.ach and summarize any validation issues."
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
An MCP (Model Context Protocol) server for parsing and validating NACHA/ACH files.
Node.js 18 or later
npm
Related MCP server: acmt001-mcp
git clone https://github.com/msuresh007/nacha-mcp.git
cd nacha-mcp
npm install
npm run buildThis compiles src/ to dist/. Re-run npm run build after pulling any updates.
A small, arithmetically-valid sample file is included at examples/sample.ach. Once built,
you can run either tool directly from the command line without an MCP client, to confirm
everything works:
node -e "const {analyzeNachaFile}=require('./dist/analyze.js');const fs=require('fs');console.log(JSON.stringify(analyzeNachaFile(fs.readFileSync('examples/sample.ach','utf-8')),null,2))"You should see "valid": true with an empty issues array, one batch, and one entry.
parse_nacha_file — Parses a NACHA file at a given path into full structured JSON: file header, batches (header, entries with addenda, control), and file control.
summarize_nacha_file — Parses a NACHA file and returns a condensed summary: batch count, total entries, total debit/credit amounts, SEC codes present, and validation issues.
Both tools take a single input, file_path, an absolute path to the file on disk.
Parsing includes:
Structural validation (record length, record type ordering, batch header/control pairing).
Arithmetic validation — entry hash, debit/credit totals, and entry/addenda counts are recomputed from the actual entries and cross-checked against the declared Batch Control and File Control values. Mismatches are reported as validation issues rather than silently accepted.
IAT (International ACH Transaction) batches and addenda type codes 10-18.
npm startThe server communicates over stdio using the MCP protocol; it's not meant to be run interactively on its own. Use it through an MCP client as described below.
From the project directory, after building:
claude mcp add nacha -- node "$(pwd)/dist/index.js"(On Windows PowerShell: claude mcp add nacha -- node "$PWD\dist\index.js")
Create .vscode/mcp.json in the project you want to use it from (or add to it if it already
exists), replacing the path with the absolute path to your clone of this repo:
{
"servers": {
"nacha": {
"type": "stdio",
"command": "node",
"args": ["/absolute/path/to/nacha-mcp/dist/index.js"]
}
}
}Alternatively, run MCP: Add Server from the Command Palette (Ctrl+Shift+P /
⇧⌘P), choose Workspace, and point it at node with the same args — VS Code
writes the same .vscode/mcp.json for you.
Once saved, open Copilot Chat, switch to Agent mode, and the parse_nacha_file /
summarize_nacha_file tools will be available (VS Code starts the server on demand).
Add an entry to the client's MCP server config (e.g. claude_desktop_config.json),
replacing the path with the absolute path to your clone of this repo:
{
"mcpServers": {
"nacha": {
"command": "node",
"args": ["/absolute/path/to/nacha-mcp/dist/index.js"]
}
}
}Restart the client after adding the config.
src/constants.ts — SEC codes, transaction codes, ISO country/currency lookups.
src/format.ts — money/date/time field parsing.
src/parser.ts — structural validation and record parsing (file/batch/entry/addenda).
src/validate.ts — arithmetic validation (hashes, totals, counts).
src/analyze.ts — combines parsing and arithmetic validation.
src/summarize.ts — condensed summary view.
src/index.ts — MCP server and tool registration.
No unit tests are included by design — this is meant to stay a small, easily auditable server.
MIT — see LICENSE.
Parses a NACHA (ACH) fixed-width file into structured JSON: file header, batches (header, entries with addenda, control), and file control. Validates record structure and cross-checks entry hashes, debit/credit totals, and record counts, reporting any mismatches as issues.
| Name | Required | Description | Default |
|---|---|---|---|
| file_path | Yes | Absolute path to the NACHA/ACH file on disk. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the burden. It discloses validation behavior well: cross-checking record counts, hashes, and debit/credit totals, and reporting mismatches as 'issues'. It could add a bit more about error behavior for unreadable or malformed files, but the existing detail is substantial.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two tight sentences, each carrying essential information: the first defines the output structure, the second the validation behavior. It is front-loaded with the core action and resource. No filler or repetition.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given one parameter, no annotations, and no output schema, the description is remarkably complete: it lists the CSV JSON composition, the validation checks, and the reporting of issues. An agent can confidently call the tool knowing what input to provide and what to do with the result.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
There is only one parameter and its schema description is 100% complete ('Absolute path to the NACHA/ACH file on disk'). The tool description does not add anything about the parameter beyond the schema, but with full schema coverage the baseline of 3 is appropriate.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb ('Parses') and resource ('NACHA/ACH fixed-width file') and names the output structure explicitly (file header, batches, control). It also distinguishes itself from sibling summarize_nacha_file by emphasizing structured JSON extraction plus validation rather than summarization.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description conveys the natural use case—get structured JSON from a NACHA file—but it does not explicitly contrast with summarize_nacha_file or state when the agent should choose parsing over summarizing. Usage context is implied clearly by the verb and output, but there is no explicit when/when-not guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Parses a NACHA (ACH) file and returns a condensed summary: batch count, total entries, total debit/credit amounts, SEC codes present, and validation issues, without dumping every field of every record.
| Name | Required | Description | Default |
|---|---|---|---|
| file_path | Yes | Absolute path to the NACHA/ACH file on disk. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full safety burden. It clearly states it parses and returns a summary, implying a read-only operation, and notes that it reports validation issues. However, it does not explicitly state side-effect-free behavior or potential error conditions on malformed files.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
A single, tightly packed sentence that front-loads the verb and resource, then enumerates specific output elements. No wasted words, and the critical exclusion is stated compactly.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple one-parameter tool with no output schema, the description adequately specifies its return content with field-level detail. It falls just short of being fully complete by not describing the result structure or behavior on invalid files, though those gaps are minor.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100% and the single file_path parameter is well-documented in the schema. The description does not add meaning beyond the schema, which is fine at the baseline of 3.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description states a specific action ('Parses... and returns') and explicitly lists the summary contents: batch count, total entries, total debit/credit amounts, SEC codes, and validation issues. The phrase 'without dumping every field of every record' clearly differentiates it from the sibling parse_nacha_file.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description explicitly frames when to use this tool: when a condensed summary is desired rather than full record-level detail. The contrast 'without dumping every field' effectively communicates the when-not and implicitly routes to the sibling for detailed extraction.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
v0.1.0parse_nacha_filesummarize_nacha_fileScored across 2 tools
The two tools have clearly different outputs—one returns the full parsed structure and one returns a condensed summary—so an agent can pick based on response size. There is mild overlap because both parse the file, but the naming and descriptions sufficiently differentiate their purposes.
Both tool names follow the same verb_noun_file pattern: parse_nacha_file and summarize_nacha_file. The naming is predictable, consistent, and accurately reflects the intent of each tool.
With only two tools, the server is intentionally narrow, but both tools serve a clear and distinct purpose for NACHA file handling. The count is slightly thin but not inappropriate given the focused read-only scope.
For a server focused on reading and validating NACHA files, the surface covers the essential workflows: full detailed parsing and condensed summarization. It could benefit from additional capabilities like file creation or export, but those seem outside its apparent scope.
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