# MCP server

Also written model context protocol server.

*https://stockmarketstack.com/glossary/mcp-server · next to Financial MCP Servers & AI Agents*

**Definition:** A process that exposes tools, resources and prompts to a model client over the Model Context Protocol, so a language model can call them without anyone writing a client. It is a connector and nothing more: it grants no rights to the data behind it, holds no subscription of its own, and changes neither the price nor the licence of what it returns.

## How it works

The Model Context Protocol connects model applications to outside data and tools over JSON-RPC 2.0.
Its specification names three roles, and keeping them apart is most of understanding the term.
**Hosts** are the applications that initiate connections — a chat application, an editor, an agent
framework. **Clients** are the connectors inside a host, one per server. **Servers** are the
processes that provide context and capabilities.

A server may offer three kinds of thing: resources, described as context and data for the user or the
model to use; prompts, templated messages and workflows for users; and tools, functions for the model
to execute. Financial servers are almost entirely the third — a set of callable operations such as
fetching a quote or a filing, each with a schema the client reads at connection time. That is the
actual gain over the REST API underneath: nobody writes a client, and one question can cross several
tools without a script joining them.

Two things about the plumbing decide whether a given client can talk to a given server at all.

**The transport.** Two standard ones are defined. With stdio the server runs as a subprocess the
client launched, speaking newline-delimited messages over its standard streams — the process is on
your machine, holding your key. With Streamable HTTP each message is posted to one HTTP endpoint and
replies arrive as a JSON object or a request-scoped stream — the server is somewhere else, run by
somebody else. The semantics are identical across both, so this is a deployment and licensing
decision rather than a functional one.

**The revision.** Protocol versions are dates, not numbers: identifiers are in `YYYY-MM-DD` form "to
indicate the last date backwards incompatible changes were made", and the revision current when this
page was last checked was 2026-07-28. That string is what to look for in a server's documentation and
in a client's release notes, because a mismatch is the ordinary reason a correctly configured server
does not appear.

## What it is not

Four things the word does not mean, each of which is a mistake somebody has made on the strength of
it.

**Not a data licence.** The protocol moves data into a chat window; it grants nothing. A server
wrapping a vendor's API needs that vendor's key and inherits that vendor's terms exactly.
[Financial MCP servers, and the licence behind them](https://stockmarketstack.com/guides/mcp-and-financial-data) works through
what three exchanges have published about AI use, which is the part with a bill attached.

**Not a hosted API.** A server is a component you install or point at, not a service with its own
coverage, uptime or pricing. Where a card lists both an API and a server, they are one product and one
subscription with two front doors.

**Not an agent.** The server exposes tools and answers calls. The host decides which servers are
connected, which tools the model sees, and whether a person is asked before one is invoked — and the
specification is blunt that it "cannot enforce these security principles at the protocol level". It
also warns that descriptions of tool behaviour "should be considered untrusted, unless obtained from a
trusted server". The judgement lives in the host, not in the server.

**Not a change to what the data costs.** A delayed feed read through a server is still delayed. A
quote that was display-use on a screen may be something else once a process consumes it, which is the
[non-display use](https://stockmarketstack.com/glossary/non-display-use) question, and a quote that reaches somebody who is not
you is the [redistribution](https://stockmarketstack.com/glossary/redistribution) one. Neither is altered by the protocol carrying
it.

## Why it matters here

This is the most-used phrase in the catalogue, and it is used about cards that differ in ways the
phrase hides. Three checks before treating two servers as comparable.

**Read-only or not.** [SEC EDGAR MCP](https://stockmarketstack.com/tools/sec-edgar-mcp) reads a public source and needs no key.
[SnapTrade](https://stockmarketstack.com/tools/snaptrade)'s server is read-only and scoped to accounts.
[QuantConnect](https://stockmarketstack.com/tools/quantconnect)'s can create projects, run backtests and deploy live algorithms.
The failure modes that are tolerable against a read tool are not tolerable against a write one, and
the category listing at [MCP servers and AI agents](https://stockmarketstack.com/categories/mcp-ai-agents) marks which is which.

**Where it runs, and therefore who sees your key and your queries.** A server you host exposes the
data to one third party, the model provider that has to see a tool result to answer. A hosted server
adds a second party, who holds your key. For anything licensed that is the decision rather than a
detail; [OpenBB](https://stockmarketstack.com/tools/openbb) running locally over your own provider keys is the shape to compare
against.

**Whether a server is the whole product or an accessory to one.** Every card in the catalogue that
ships one is listed at [tools with MCP](https://stockmarketstack.com/tools-with-mcp), and for most of them the server is a feature
of a subscription that existed first. A server is a dependency, chosen the way any dependency is: what
it wraps, who maintains it, and which protocol revision it tracks.

## Where you will meet this

- [SEC EDGAR MCP](https://stockmarketstack.com/tools/sec-edgar-mcp.md)
- [OpenBB](https://stockmarketstack.com/tools/openbb.md)
- [tradingview-mcp](https://stockmarketstack.com/tools/tradingview-mcp.md)
- [MaverickMCP](https://stockmarketstack.com/tools/maverick-mcp.md)
- [SnapTrade](https://stockmarketstack.com/tools/snaptrade.md)
- [QuantConnect](https://stockmarketstack.com/tools/quantconnect.md)
- [2iQ Insider Transactions Data](https://stockmarketstack.com/tools/2iq-insider-data.md)
- [AI Hedge Fund](https://stockmarketstack.com/tools/ai-hedge-fund.md)
- [Alpaca Market Data](https://stockmarketstack.com/tools/alpaca-market-data.md)
- [Alpha Vantage](https://stockmarketstack.com/tools/alpha-vantage.md)
- [AlphaSense](https://stockmarketstack.com/tools/alphasense.md)
- [AskNews](https://stockmarketstack.com/tools/asknews.md)

## FAQ

### Is an MCP server the same thing as a data subscription?

No, and conflating the two is the expensive mistake. Almost every financial server in this catalogue is a wrapper over an API its vendor already published, and most refuse to start without that vendor's key. The server is the connector; the subscription behind the key is the purchase, at the same price and under the same terms as before.

### Why will a server not connect to my client?

Usually the transport or the protocol revision. A server built for stdio expects to be launched as a subprocess by the client; one built for Streamable HTTP expects to be reached at an endpoint. Protocol revisions are dates rather than version numbers, and a client and server have to negotiate one they share, so check which date each of them supports.

## Sources

1. [Specification (revision 2026-07-28)](https://modelcontextprotocol.io/specification/2026-07-28) — Model Context Protocol, 2026-07-28
2. [Transports: Overview](https://modelcontextprotocol.io/specification/2026-07-28/basic/transports) — Model Context Protocol, 2026-07-28
3. [Versioning](https://modelcontextprotocol.io/specification/versioning) — Model Context Protocol, read 2026-09-14

*Last updated 2026-09-21. A reference page, corrected in place — not a dated post.*