Add GateCore integration page

integrations/gatecore.md

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+---
+layout: integration
+name: GateCore
+description: Discover and procure governed AI capabilities from the GateCore marketplace, with machine-readable price, scope, and trust terms on every listing.
+authors:
+    - name: GateCore AI
+      socials:
+        github: GateCoreAI-com
+repo: https://github.com/GateCoreAI-com/gatecore-mcp
+type: Tool Integration
+report_issue: https://github.com/GateCoreAI-com/gatecore-mcp/issues
+version: Haystack 2.0
+toc: true
+---
+
+### **Table of Contents**
+
+- [Overview](#overview)
+- [Installation](#installation)
+- [Usage](#usage)
+- [Examples](#examples)
+- [License](#license)
+
+## Overview
+
+[GateCore](https://gatecoreai.com) is the governed transaction layer for AI agents. Every agent request is identity-verified, policy-checked, priced, settled, and receipted on a tamper-evident ledger before it touches tools, data, or money.
+
+This integration connects Haystack pipelines and Agents to the GateCore marketplace through GateCore's public MCP server, using Haystack's native MCP support ([`MCPTool`](https://docs.haystack.deepset.ai/docs/mcptool) and [`MCPToolset`](https://docs.haystack.deepset.ai/docs/mcptoolset) from the [`mcp-haystack`](https://pypi.org/project/mcp-haystack/) package). Your Haystack agent can:
+
+- **Discover governed capabilities.** `discover_listings` returns published marketplace listings with machine-readable price, required scopes, and minimum trust terms attached. No key and no account required.
+- **Read the contract before committing.** `get_listing` returns one listing and its machine-enforceable contract: price in cents, required scopes, minimum trust, target, and data classification. The agent evaluates terms programmatically instead of parsing marketing copy.
+- **Request governed procurement.** With a GateCore MCP access key (`gcmk_` prefix), `procure` returns a PROCURE, REVIEW, or DENY decision, and every decision produces a signed, independently verifiable receipt.
+
+The MCP endpoint is `https://mcp.gatecoreai.com/mcp` (streamable HTTP). The server manifest lives at `https://mcp.gatecoreai.com/.well-known/mcp.json`, and the [gatecore-mcp repository](https://github.com/GateCoreAI-com/gatecore-mcp) carries the quickstart and runnable client examples.
+
+## Installation
+
+The integration uses Haystack's official MCP tooling:
+
+```bash
+pip install mcp-haystack
+```
+
+## Usage
+
+Point an `MCPTool` at GateCore's public endpoint and call a discovery tool directly. Discovery is anonymous: no key, no account.
+
+```python
+from haystack_integrations.tools.mcp import MCPTool, StreamableHttpServerInfo
+
+server_info = StreamableHttpServerInfo(url="https://mcp.gatecoreai.com/mcp")
+
+discover = MCPTool(name="discover_listings", server_info=server_info)
+
+# All arguments are optional filters: query, tags, max_price_cents, min_trust
+result = discover.invoke(max_price_cents=500)
+print(result)
+```
+
+Fetch the full machine-enforceable contract for a listing found in discovery:
+
+```python
+get_listing = MCPTool(name="get_listing", server_info=server_info)
+
+listing = get_listing.invoke(listing_id="listing:example-capability")
+print(listing)
+```
+
+The returned contract carries the price in cents, the required scopes, the minimum trust threshold, the target, and the data classification, so the agent can decide whether to proceed without a human reading a sales page.
+
+## Examples
+
+### Give a Haystack Agent the GateCore marketplace tools
+
+`MCPToolset` loads the marketplace tools as a single unit. Filter with `tool_names` so the agent sees only what it needs:
+
+```python
+from haystack import Pipeline
+from haystack.components.agents import Agent
+from haystack.components.generators.chat import OpenAIChatGenerator
+from haystack.dataclasses import ChatMessage
+from haystack_integrations.tools.mcp import MCPToolset, StreamableHttpServerInfo
+
+server_info = StreamableHttpServerInfo(url="https://mcp.gatecoreai.com/mcp")
+
+toolset = MCPToolset(
+    server_info=server_info,
+    tool_names=["discover_listings", "get_listing"],
+)
+
+pipeline = Pipeline()
+pipeline.add_component(
+    "agent",
+    Agent(chat_generator=OpenAIChatGenerator(model="gpt-4o-mini"), tools=toolset),
+)
+
+result = pipeline.run(
+    {
+        "agent": {
+            "messages": [
+                ChatMessage.from_user(
+                    "Find marketplace listings under five dollars and summarize "
+                    "their price, required scopes, and trust terms."
+                )
+            ]
+        }
+    }
+)
+print(result["agent"]["messages"][-1].text)
+```
+
+### Governed procurement
+
+The `procure`, `list_procurements`, and `submit_lead` tools require a GateCore MCP access key sent as a bearer token (`Authorization: Bearer gcmk_<your-key>`). Without a key these tools fail closed with a tool-level refusal. Every governed decision produces an Ed25519-signed receipt that binds the request, the policy decision, and the settlement together; receipts verify entirely client-side at [gatecoreai.com/verify](https://gatecoreai.com/verify) with no account and no callback to GateCore.
+
+See the [quickstart](https://github.com/GateCoreAI-com/gatecore-mcp/blob/main/QUICKSTART.md) for the full tool reference and copy-pasteable calls.
+
+## License
+
+The GateCore public MCP integration surface is distributed under the MIT license.