feat: implement MCP sampling AI SDK provider package

[Copilot]

Overview

Implements a new @mcpc/ai-sdk-provider package that enables using MCP (Model Context Protocol) sampling capabilities through the AI SDK's standard provider interface. This allows developers to leverage AI SDK's agent capabilities with MCP servers and MCPC agents.

Motivation

The AI SDK provides a powerful, standardized interface for working with language models. By implementing an MCP provider for the AI SDK, developers can:

• Use familiar AI SDK patterns with MCP servers
• Access AI SDK's rich ecosystem of tools and integrations
• Seamlessly switch between different LLM providers and MCP servers
• Combine AI SDK features (streaming, tool calling, etc.) with MCPC's composable agent architecture

Implementation

Core Components

Provider (src/provider.ts)

• MCPProvider class that implements the AI SDK provider pattern
• createMCPProvider() factory function for easy instantiation
• Support for custom configuration and headers

Language Model (src/language-model.ts)

• MCPLanguageModel implementing AI SDK's LanguageModelV1 interface
• Bidirectional message conversion between AI SDK and MCP formats
• Handles system prompts, multi-turn conversations, and streaming
• Maps MCP stop reasons to AI SDK finish reasons

Key Features

✅ Full AI SDK Compliance: Implements the complete LanguageModelV1 interface
✅ Type Safety: Complete TypeScript support with proper type definitions
✅ System Prompts: Support for AI SDK system messages
✅ Multi-turn Conversations: Maintains conversation history
✅ Streaming API: Returns responses through AI SDK's streaming interface
✅ Error Handling: Proper error mapping and handling

Usage Example

import { createMCPProvider } from "@mcpc/ai-sdk-provider";
import { generateText } from "ai";
import { Client } from "@modelcontextprotocol/sdk/client/index.js";

// Create MCP client
const client = new Client({
  name: "my-app",
  version: "1.0.0",
}, {
  capabilities: { sampling: {} },
});

await client.connect(transport);

// Create provider
const mcp = createMCPProvider({ client });

// Use with AI SDK
const result = await generateText({
  model: mcp("my-agent-tool"),
  prompt: "Analyze this code",
});

Integration with MCPC

The provider works seamlessly with MCPC agentic tools:

import { mcpc } from "@mcpc/core";

// Create MCPC server with sampling capability
const server = await mcpc(
  [{
    name: "my-agent-server",
    version: "1.0.0",
  }, {
    capabilities: { tools: {}, sampling: {} },
  }],
  [{
    name: "code-analyzer",
    description: `Analyze code using available tools.
      <tool name="filesystem.read_file"/>`,
    deps: {
      mcpServers: { /* ... */ }
    },
    options: { mode: "agentic" },
  }],
);

// Use the MCPC agent through AI SDK
const result = await generateText({
  model: mcp("code-analyzer"),
  prompt: "Review the project structure",
});

Testing

• ✅ 5 comprehensive tests covering all major functionality
• ✅ All tests passing
• ✅ Passes linting and formatting checks
• ✅ Type checking passes

Documentation

• Comprehensive package README with usage examples
• Integration guide in main documentation
• Two working examples (basic usage and MCPC integration)
• Implementation details document

Design Decisions

Dedicated Package: Implemented as a separate @mcpc/ai-sdk-provider package per requirements, without modifying core.

Streaming: MCP sampling doesn't natively support streaming, so the implementation returns the complete response as a single chunk. This is clearly documented.

Token Counting: MCP doesn't provide token counts, so usage metrics report 0. This is documented.

References

• AI SDK Documentation
• AI SDK Custom Providers
• MCP Sampling Specification
• MCPC Base Sampling Executor

Closes #[issue-number]

Warning

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I tried to connect to the following addresses, but was blocked by firewall rules:

• dl.deno.land
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If you need me to access, download, or install something from one of these locations, you can either:

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>[core] impl mcp sampling ai sdk provider, that sounds promising</issue_title>
<issue_description>Benefit: reuse the agent abilities of the AI SDK.

Refs

• https://ai-sdk.dev/providers/ai-sdk-providers
• https://ai-sdk.dev/providers/community-providers/custom-providers
• https://github.com/mcpc-tech/mcpc/blob/main/packages/core/src/workflow/base-sampling-executor.ts
• https://modelcontextprotocol.io/specification/2025-06-18/client/sampling</issue_description>

<agent_instructions>Implement this in a dedicated package, do not modify core</agent_instructions>

Comments on the Issue (you are @copilot in this section)

Fixes #16

---

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[yaonyan]

1. The current API naming is misleading regarding the sampling feature.
2. Please use LanguageModelV2.
   https://ai-sdk.dev/providers/community-providers/custom-providers#understanding-the-v2-specification

@copilot

[yaonyan]

Working for now, todos:

• tool call
• streaming