MCP Integration¶

Assay is built for the Model Context Protocol.

What is MCP?¶

Model Context Protocol (MCP) is an open standard for connecting AI agents to external tools and data sources. It defines how agents:

Discover available tools (tools/list)
Call tools with arguments (tools/call)
Receive results

Assay validates these interactions to ensure your agent behaves correctly.

Assay's Role in the MCP Stack¶

┌─────────────────────────────────────────────────────────────┐
│                        Your Agent                           │
└─────────────────────────────────────────────────────────────┘
                              │
                              ▼
┌─────────────────────────────────────────────────────────────┐
│                     MCP (Connectivity)                      │
│              "How agents talk to tools"                     │
└─────────────────────────────────────────────────────────────┘
                              │
                              ▼
┌─────────────────────────────────────────────────────────────┐
│                   Assay (Quality Engineering)               │
│        "Are those conversations correct, safe, repeatable?" │
└─────────────────────────────────────────────────────────────┘
                              │
                              ▼
┌─────────────────────────────────────────────────────────────┐
│                      External Tools                         │
│              Databases, APIs, File Systems                  │
└─────────────────────────────────────────────────────────────┘

MCP without Assay = unverified traffic.

Integration Patterns¶

Assay integrates with MCP in three ways:

1. Trace Consumer (Offline Testing)¶

Import MCP sessions and run deterministic tests in CI.

assay import --format inspector session.json
assay run --config eval.yaml --strict

Use case: CI regression gates, debugging, baseline comparison.

Quick Start

2. MCP Wrapper (Runtime Validation)¶

Expose Assay as MCP tools that agents call before executing actions.

assay mcp wrap --policy assay.yaml -- <real-mcp-command> [args...]

The agent can query: - assay_check_args — "Is this argument valid?" - assay_check_sequence — "Is this call order allowed?" - assay_policy_decide — "Should I proceed?"

Use case: Agent self-correction, runtime guardrails.

Server Guide

3. MCP Gateway (Enterprise)¶

Inline enforcement for production deployments.

Agent ──► Assay Gateway ──► MCP Server ──► Tools
              │
              └─► Capture, Redact, Enforce, Sign

Use case: Compliance logging, policy enforcement, audit trails.

Gateway Guide (Enterprise)

What Assay Validates¶

MCP standardizes how agents communicate. Assay validates what they communicate.

Validation	Question	Metric
Argument Correctness	Are tool arguments schema-valid?	`args_valid`
Sequence Validity	Are calls in the right order?	`sequence_valid`
Blocklist Enforcement	Was a forbidden tool called?	`tool_blocklist`
Replay Fidelity	Can we reproduce this incident?	`replay`

Supported Formats¶

Import Formats¶

Format	Source	Command
MCP Inspector	MCP Inspector	`--format inspector`
JSON-RPC 2.0	Raw MCP messages	`--format jsonrpc`
LangChain	LangChain traces	Not yet supported in `assay import`
LlamaIndex	LlamaIndex traces	Not yet supported in `assay import`

Export Formats¶

Format	Use Case	Flag
SARIF	GitHub Code Scanning	`assay ci --sarif <path>`
JUnit	CI test results	`assay ci --junit <path>`
JSON	Programmatic access	`assay validate --format json --output <path>`

Quick Comparison¶

Feature	MCP Alone	MCP + Assay
Tool discovery	✅	✅
Tool execution	✅	✅
Argument validation	❌	✅
Sequence enforcement	❌	✅
Blocklist	❌	✅
Deterministic replay	❌	✅
CI integration	❌	✅
Offline testing	❌	✅

Next Steps¶

Quick Start

Import your first MCP session in 5 minutes.

Quick Start
Assay MCP Wrapper

Let agents validate their own actions.

Server Guide
Self-Correction

Build agents that fix their own mistakes.

Self-Correction
Import Formats

Supported log formats and conversion.

Import Formats