Overview

IRS Form 990 data for 1.8M+ tax-exempt organizations, via the ProPublica Nonprofit Explorer API. Search by name, fetch an org's financial snapshot, and pull its full filing history from any MCP client. Runs as a stdio process, a local Streamable HTTP server, or the public hosted endpoint above.

Tools

Capability reference

nonprofit_search _tool

• Full-text query — supports quoted phrases ("Red Cross"), required terms (+evanston), excluded terms (-dental)
• Optional filters: US state/territory or military postal code (ZZ for foreign entities; a code outside that set is rejected rather than silently returning national results), NTEE major sector (1–10), 501(c) subsection code (3 covers both public charities and private foundations — see foundation_type on nonprofit_get_organization to tell them apart)
• Paginated at 25 per page (page, zero-indexed); num_pages, per_page, and page_offset track position
• API caps total results at 10,000 — total_results === 10000 means the actual count may be higher, and a page whose offset reaches that ceiling is refused (pagination_ceiling)
• Zero matches and a page past the last one both succeed with an empty organizations array and a notice explaining which case it is
• Returns EINs — pass to nonprofit_get_organization or nonprofit_get_filings for details

nonprofit_get_organization _tool

• Accepts EIN as integer (530196605) or string with or without hyphen ("53-0196605"); use nonprofit_search first if you only have an org name
• Returns legal identity, address, NTEE code, 501(c) type, and IRS ruling date
• IRS Business Master File standing: deductibility (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, plus the source PDF link
• 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

nonprofit_get_filings _tool

• All Form 990 filings with extracted data, sorted newest first — per filing: revenue, expenses, assets, liabilities, net assets, revenue breakdown (contributions, program service, investment income), and the source PDF link
• 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
• filings_pdf_only lists older filings with a PDF but no extracted data
• An EIN that resolves to a real org with no 990 on record returns an empty filings array plus a notice, not an error
• Data lags 1–2 years — always cite tax_prd_yr (fiscal year) when presenting figures

Features

Built on @cyanheads/mcp-ts-core: stdio and Streamable HTTP transports, pluggable auth (none / jwt / oauth), swappable storage (in-memory, filesystem, Supabase, Cloudflare KV/R2/D1), structured logging with optional OpenTelemetry tracing.

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"
    }
  }
}

Self-Hosted / Local

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:

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:

  sh

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

• Run checks and tests:

  sh

  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

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 are welcome. Run checks and tests before submitting:

bun run devcheck
bun run test

License

Apache-2.0 — see LICENSE for details.