Nonprofit Explorer Mcp Server

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Tools

3 tools for working with US nonprofit and IRS Form 990 data:

Tool	Description
nonprofit_search	Search 1.8M+ IRS-recognized tax-exempt organizations by name, keyword, city, or phrase with optional state, NTEE sector, and 501(c) filters
nonprofit_get_organization	Full profile for one org by EIN: legal identity, IRS classification, ruling date, and a financial snapshot from the most recent Form 990
nonprofit_get_filings	All Form 990 filings for an org by EIN: year-by-year financials, revenue breakdown, executive compensation, and source PDF links

nonprofit_search

Search for tax-exempt organizations across the IRS Nonprofit Explorer dataset.

• Full-text search across org name, the IRS Business Master File secondary name line, and city with relevance ranking
• Supports quoted phrases ("Red Cross"), required terms (+evanston), excluded terms (-dental)
• Filter by US state, territory, or military postal code (ZZ for foreign entities); case-insensitive, and a code outside that set is rejected rather than silently returning national results
• Filter by NTEE major sector (Arts, Education, Health, Human Services, etc., 1–10)
• Filter by 501(c) subsection code (e.g., 3 = charitable organization — both public charities and private foundations, 4 = social welfare)
• Paginated at 25 per page; use page (zero-indexed) with num_pages, per_page, and page_offset to walk large result sets
• Zero matches and a page past the last one are both successful searches with an empty organizations array and a notice explaining which case it is
• API caps total results at 10,000; total_results === 10000 means the actual count may be higher, and a page whose offset reaches 10,000 is refused with the pagination_ceiling error
• Returns EINs — pass to nonprofit_get_organization or nonprofit_get_filings for details

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nonprofit_get_organization

Fetch the full profile for a single tax-exempt org by EIN.

• Accepts EIN as integer (530196605) or string with or without hyphen ("53-0196605")
• Returns legal name, address, NTEE code, 501(c) type, and IRS ruling date
• IRS Business Master File standing: whether contributions are deductible (including the deductible-by-treaty case), exemption status, and public-charity vs. private-foundation classification — each decoded from its IRS code with the raw code retained
• Financial snapshot from the most recent Form 990: revenue, expenses, assets, liabilities, net assets
• Includes source 990 PDF link and IRS Business Master File summary figures
• filing_count shows how many filings with extracted data are on record
• Data lags 1–2 years; tax_prd_yr in the snapshot is the fiscal year of the filing, not the current year
• Use nonprofit_search first if you only have an org name

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nonprofit_get_filings

Fetch the full filing history for an org by EIN.

• All Form 990 filings with extracted financial data, sorted newest first
• Per-filing: revenue, expenses, assets, liabilities, net assets, revenue breakdown (contributions, program service, investment income)
• program_expense_ratio is always null — ProPublica returns no Form 990 Part IX program-service expense total, so the program/management/fundraising split is only in the source PDF
• Executive compensation summary with field-name transparency and a note pointing to Schedule J for per-officer detail
• Source 990 PDF link per filing
• An EIN that resolves to a real org with no 990 on record returns an empty filings array plus a notice — a successful lookup, not an error
• filings_pdf_only lists older filings with a PDF but no extracted data
• Data lags 1–2 years; always cite tax_prd_yr (fiscal year) when presenting figures

Features

Built on @cyanheads/mcp-ts-core:

• Declarative tool definitions — single file per tool, framework handles registration and validation
• Unified error handling — handlers throw, framework catches, classifies, and formats
• Pluggable auth: none, jwt, oauth
• Swappable storage backends: in-memory, filesystem, Supabase, Cloudflare KV/R2/D1
• Structured logging with optional OpenTelemetry tracing
• STDIO and Streamable HTTP transports

ProPublica Nonprofit Explorer / IRS-specific:

• Keyless access — ProPublica Nonprofit Explorer API requires no API key
• Covers 1.8M+ IRS-recognized tax-exempt organizations
• IRS Form 990 data: annual filings for public charities (990), small orgs (990-EZ), and private foundations (990-PF)
• Source filing PDF link on every filing record, except where IRS PDF processing lags the extracted data and pdf_url is still null
• Data sourced from ProPublica Nonprofit Explorer, derived from IRS Form 990 filings; data lags 1–2 years

Agent-friendly output:

• Provenance on every response — data_source attribution on all tool outputs, ProPublica URL for direct verification
• Filing-year clarity — tax_prd_yr prominently labeled as fiscal year with explicit lag caveat in every financial response
• Null values are rendered, not dropped — the formatted text names why a value is absent (never recorded by the IRS, not extracted from the filing, not carried by that form type), and structuredContent keeps an explicit null rather than omitting the key
• Field-name transparency on compensation — field_name and form_type exposed so agents know exactly which IRS field was read

Getting started

Public Hosted Instance

A public instance is available at https://nonprofit-explorer.caseyjhand.com/mcp — no installation required. Point any MCP client at it via Streamable HTTP, with this client config:

{
  "mcpServers": {
    "nonprofit-explorer-mcp-server": {
      "type": "streamable-http",
      "url": "https://nonprofit-explorer.caseyjhand.com/mcp"
    }
  }
}

Or, install locally and add the following to your MCP client configuration file.

{
  "mcpServers": {
    "nonprofit-explorer-mcp-server": {
      "type": "stdio",
      "command": "bunx",
      "args": ["@cyanheads/nonprofit-explorer-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "MCP_LOG_LEVEL": "info"
      }
    }
  }
}

Or with npx (no Bun required):

{
  "mcpServers": {
    "nonprofit-explorer-mcp-server": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@cyanheads/nonprofit-explorer-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "MCP_LOG_LEVEL": "info"
      }
    }
  }
}

Or with Docker:

{
  "mcpServers": {
    "nonprofit-explorer-mcp-server": {
      "type": "stdio",
      "command": "docker",
      "args": [
        "run", "-i", "--rm",
        "-e", "MCP_TRANSPORT_TYPE=stdio",
        "ghcr.io/cyanheads/nonprofit-explorer-mcp-server:latest"
      ]
    }
  }
}

For Streamable HTTP, set the transport and start the server:

MCP_TRANSPORT_TYPE=http MCP_HTTP_PORT=3010 bun run start:http
# Server listens at http://localhost:3010/mcp

Prerequisites

• Bun v1.3.14 or higher (or Node.js v24+).
• No API key required — ProPublica Nonprofit Explorer is a keyless public API.

Installation

1. Clone the repository:

git clone https://github.com/cyanheads/nonprofit-explorer-mcp-server.git

2. Navigate into the directory:

cd nonprofit-explorer-mcp-server

3. Install dependencies:

bun install

4. Configure environment:

cp .env.example .env
# edit .env as needed (no required vars — server works out of the box)

Configuration

All configuration is validated at startup. Key environment variables:

Variable	Description	Default
MCP_TRANSPORT_TYPE	Transport: stdio or http	stdio
MCP_HTTP_PORT	HTTP server port	3010
MCP_HTTP_HOST	HTTP server hostname	127.0.0.1
MCP_HTTP_ENDPOINT_PATH	HTTP endpoint path	/mcp
MCP_PUBLIC_URL	Public origin override for TLS-terminating reverse-proxy deployments	—
MCP_AUTH_MODE	Authentication: none, jwt, or oauth	none
MCP_LOG_LEVEL	Log level (debug, info, warning, error, etc.)	info
LOGS_DIR	Directory for log files (Node.js only)	<project-root>/logs
STORAGE_PROVIDER_TYPE	Storage backend: in-memory, filesystem, supabase, cloudflare-kv/r2/d1	in-memory
OTEL_ENABLED	Enable OpenTelemetry instrumentation	false

No server-specific required variables. ProPublica Nonprofit Explorer is a keyless public API.

See .env.example for the full list of optional overrides.

Running the server

Local development

• Build and run:

  # One-time build
  bun run rebuild
  
  # Run the built server
  bun run start:stdio
  # or
  bun run start:http
  

• Run checks and tests:

  bun run devcheck   # Lint, format, typecheck, security
  bun run test       # Vitest test suite
  bun run lint:mcp   # Validate MCP definitions against spec
  

Docker

docker build -t nonprofit-explorer-mcp-server .
docker run --rm -p 3010:3010 nonprofit-explorer-mcp-server

The Dockerfile defaults to HTTP transport, stateless session mode, and logs to /var/log/nonprofit-explorer-mcp-server. OpenTelemetry peer dependencies are installed by default — build with --build-arg OTEL_ENABLED=false to omit them.

Project structure

Directory	Purpose
src/index.ts	createApp() entry point — registers tools and inits the service.
src/mcp-server/tools	Tool definitions (*.tool.ts). Three tools for search and financial data.
src/services/nonprofit-explorer	ProPublica Nonprofit Explorer API client and domain types.
tests/	Unit and integration tests mirroring src/.

Development guide

See CLAUDE.md/AGENTS.md for development guidelines and architectural rules. The short version:

• Handlers throw, framework catches — no try/catch in tool logic
• Use ctx.log for request-scoped logging, ctx.state for tenant-scoped storage
• Register new tools via the arrays in createApp() in src/index.ts
• Wrap external API calls: validate raw → normalize to domain type → return output schema; never fabricate missing fields

Contributing

Issues and pull requests are welcome. Run checks and tests before submitting:

bun run devcheck
bun run test

License

Apache-2.0 — see LICENSE for details.