# Phoenix MCP Gateway

> One metered MCP endpoint in front of 16 MCP servers wrapping free and freemium APIs, exposing 139 tools. Each tools/call costs $0.0001 (100 micro-USD) from prepaid credits; discovery is free.

Connect over MCP Streamable HTTP to `https://gateway.mcpharbor.dev/mcp` with the header `Authorization: Bearer <your gateway API key>`. Supported protocol versions: 2026-07-28 (modern, stateless) and 2025-11-25, 2025-06-18, 2025-03-26 (legacy, `initialize` handshake). Tool names are namespaced by server, for example `arxiv__arxiv_get_metadata`. Read [agent.txt](https://gateway.mcpharbor.dev/agent.txt) before your first paid call.

## Start here

- [agent.txt](https://gateway.mcpharbor.dev/agent.txt): How to authenticate, what a call costs, which failures are safe to retry, and how to handle 402 and 429.
- [skill.txt](https://gateway.mcpharbor.dev/skill.txt): Task recipes that chain tools across servers, with the cost of each.
- [llms-full.txt](https://gateway.mcpharbor.dev/llms-full.txt): Every routable tool with its parameters, price and attribution.
- [server.json](https://gateway.mcpharbor.dev/server.json): Registry-format description of this gateway.
- [Registry API](https://gateway.mcpharbor.dev/v0.1/servers): Cursor-paginated catalog of every routable server.

## Servers

- [arXiv](https://gateway.mcpharbor.dev/docs/servers/arxiv): Search arXiv preprints and open access scholarly papers: abstracts, authors, categories 3 tools.
- [US Bureau of Labor Statistics](https://gateway.mcpharbor.dev/docs/servers/bls): US Bureau of Labor Statistics: unemployment, inflation, CPI, wages and employment series 4 tools.
- [Crossref](https://gateway.mcpharbor.dev/docs/servers/crossref): Crossref DOI metadata: citations, journals, funders, bibliometric and scholarly lookups 7 tools.
- [Europe PMC](https://gateway.mcpharbor.dev/docs/servers/europepmc): Europe PMC life science literature, open access full text index and clinical trials 24 tools.
- [Frankfurter (ECB rates)](https://gateway.mcpharbor.dev/docs/servers/frankfurter): Currency conversion and exchange rates from European Central Bank reference data 5 tools.
- [NASA Open APIs](https://gateway.mcpharbor.dev/docs/servers/nasa): NASA astronomy picture of the day and near-earth asteroid tracking from NeoWs 23 tools.
- [NOAA Tides & Currents](https://gateway.mcpharbor.dev/docs/servers/noaa_marine): NOAA tides and currents: tide predictions, water levels, sea level and marine buoy data 7 tools.
- [npm Registry](https://gateway.mcpharbor.dev/docs/servers/npm_registry): Search the npm package registry: versions, dependencies, download stats and metadata 6 tools.
- [US National Weather Service](https://gateway.mcpharbor.dev/docs/servers/nws): US National Weather Service forecasts, severe weather alerts and station observations 7 tools.
- [OpenAlex](https://gateway.mcpharbor.dev/docs/servers/openalex): OpenAlex scholarly graph: works, authors, institutions, citations, bibliometric analysis 5 tools.
- [PubChem](https://gateway.mcpharbor.dev/docs/servers/pubchem): PubChem chemistry: compound properties, molecule structures, SMILES, safety, bioassays 10 tools.
- [PubMed](https://gateway.mcpharbor.dev/docs/servers/pubmed): PubMed biomedical literature search: MeSH terms, citations, abstracts, clinical research 10 tools.
- [PyPI](https://gateway.mcpharbor.dev/docs/servers/pypi): PyPI Python package registry search: versions, dependencies, downloads, compatibility 10 tools.
- [US Treasury FiscalData](https://gateway.mcpharbor.dev/docs/servers/treasury): US Treasury fiscal data: national debt, interest rates, exchange rates, daily statements 7 tools.
- [USGS Earthquakes](https://gateway.mcpharbor.dev/docs/servers/usgs_quake): USGS earthquake catalog: seismic events, magnitude, real-time feeds and hazard data 2 tools.
- [World Bank](https://gateway.mcpharbor.dev/docs/servers/worldbank): World Bank development indicators: GDP, poverty, population, macroeconomic country data 9 tools.

## Pricing

- $0.0001 (100 micro-USD) per tool call.
- Billed on: each tools/call that reaches the upstream and returns a result.
- Free: server/discover, tools/list, registry endpoints, docs files.
- Payment: prepaid credits, drawn down per call. A call your balance cannot cover is refused with HTTP 402 before any upstream is contacted.
- A charged call that then fails upstream is refunded automatically.
- Retries are ordinary calls. There is no client idempotency key, so repeating a request that was already charged buys a second call - see [agent.txt](https://gateway.mcpharbor.dev/agent.txt), section 7.