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Bellwether MCP server

Which MCP servers are Bellwether's own, from the official registry and from asking its own domain, whether they answer, and what they offer. A program checked each of these, nobody copied them from a product page.

read 2026-10-26

← Back to Bellwether

Whose server it is
  • Registry namemarkets.bellwether/prediction-marketsverified in the MCP registry

The registry name sits under bellwether.markets. The registry only lets a publisher use that namespace after proving control of the domain through DNS or HTTP.

When we asked itchecked 2026-10-26
  • Stateanswerschecked 2026-10-26
  • Tools3
  • Server calls itselfbellwether
  • Server version1.28.1
  • Protocol version2025-06-18

On 2026-10-26 the server answered initialize and tools/list without a sign-in. First answer in 518 ms.

Should an agent connect itNot proven either way yet
  • Its tools do every use case we checked: find price spreads for the same event across Kalshi and Polymarket; list and search open markets across both venues; let AI agents query markets and spreads via MCP tools.
  • Checked on 1 of the 7 days it takes to judge reliability.

Once connected

  • For "find price spreads for the same event across Kalshi and Polymarket", the likely first call is matching_markets.
  • For "list and search open markets across both venues", the likely first call is list_markets.
  • For "let AI agents query markets and spreads via MCP tools", the likely first call is list_markets.
  • Parameters are untyped or undescribed in 3 of 3 tools: check arguments before calling.

Said by rules from the measurements above. The likely first call is a model's pick from the tool list; read its description before relying on it.

Measured dailydaily checks: 1, the first on 2026-10-26
  • INITE MCP scoreafter a weeka score needs 7 daily checks: 1 so far
  • What an agent can do with it3 of 3 use cases
  • Answeredmeasuring1 of the 7 daily checks it takes to print a share
  • Median first answer499 ms
  • Space in an agent's context≈ 241 tokensthe definitions of all its tools (3), which an agent carries on every turn
  • Tool definitionsC · 67 of 100
  • Typed results2 of 3 toolsdeclared outputSchema: results come typed, read once
  • Parameters without a description: in 3 of 3
  • Not saying whether it only reads or can destroy: 3 of 3

What an agent can do with it

  • can do · find price spreads for the same event across Kalshi and Polymarket
  • can do · list and search open markets across both venues
  • can do · let AI agents query markets and spreads via MCP tools

Each of the product's use cases, put to Jev against this server's tool list: can an agent do it with these tools?

Worth a look

None of the five warning signs in these definitions.

A program checks the server once a day: initialize and tools/list, no model. Tokens are the definitions' length at about four characters a token. The grade averages six checks of every tool's name, description, schema and annotations; it says how well the tools are described, not whether they work. The score weighs what was measured and nothing else: answering (25%), doing the product's job (25%), definitions (20%), context (10%), use (10%) and how readily a client connects (10%). A part that was not measured is left out, and a hidden instruction caps the score at 40. The state of vendors' MCP servers: method and numbers →

Tools it offers3 tools · read 2026-10-26
  • list_markets

    List open prediction markets across Kalshi and Polymarket (normalized).

  • get_market

    Get one normalized market. venue is 'kalshi' or 'polymarket'.

  • matching_markets

    Find the same real-world event on both venues, with the YES price spread.

How to connect

Add the server to your MCP client config. Claude Desktop, Cursor and most other clients read this shape:

{
  "mcpServers": {
    "prediction-markets": {
      "type": "http",
      "url": "https://api.bellwether.markets/mcp"
    }
  }
}

Add it

Claude Code, in a terminal

claude mcp add --transport http bellwether https://api.bellwether.markets/mcp

Add to CursorAdd to VS Code

claude.ai, ChatGPT and other clients: add https://api.bellwether.markets/mcp as a custom connector in the settings.

OpenAPI spec

4 paths, read 2026-10-26. Open the spec ↗

Each line is something a program found when it went looking: the registry entry, the server's own answer, a spec that parses. A missing line means we did not find it, not that it does not exist.