Wasm MCP组件执行器

Greentic MCP

Executor and component tooling for the Greentic platform targeting the wasix:mcp interface. The workspace currently provides a reusable Rust library (greentic-mcp-exec) that can load Wasm components, verify their provenance, wire in the Greentic host imports, and execute the exported MCP entrypoint.

Workspace layout

greentic-mcp/
├─ crates/
│  ├─ mcp-adapter/      # MCP adapter component template (wasix:mcp@25.06.18)
│  └─ mcp-exec/         # executor library (package: greentic-mcp-exec)
└─ Cargo.toml           # workspace manifest

greentic-mcp-exec

Public API:

use greentic_types::{EnvId, TenantCtx, TenantId};
use greentic_mcp_exec::{ExecConfig, ExecRequest, RuntimePolicy, ToolStore, VerifyPolicy};
use serde_json::json;
use std::path::PathBuf;

let tenant = TenantCtx {
    env: EnvId("dev".into()),
    tenant: TenantId("acme".into()),
    team: None,
    user: None,
    trace_id: Some("trace-123".into()),
    correlation_id: None,
    deadline: None,
    attempt: 0,
    idempotency_key: None,
};

let cfg = ExecConfig {
    store: ToolStore::LocalDir(PathBuf::from("./tools")),
    security: VerifyPolicy::default(),
    runtime: RuntimePolicy::default(),
    http_enabled: false,
    secrets_store: None,
};

let result = greentic_mcp_exec::exec(
    ExecRequest {
        component: "weather_api".into(),
        action: "forecast_weather".into(),
        args: json!({"location": "AMS"}),
        tenant: Some(tenant),
    },
    &cfg,
)?;

Key features:

• Resolver – Reads Wasm bytes from local directories or single-file HTTP sources (with caching).
• Verifier – Checks digest/signature policy before execution.
• Describe bridge – Calls the greentic:component/component@1.0.0 describe world when tools implement it, surfacing schema/default metadata directly from each component.
• Runner – Spins up a Wasmtime component environment, registers the runner-host-v1 imports from greentic-interfaces, and calls the tool's MCP exec export.
• Errors – Structured error types map resolution, verification, and runtime failures to caller-friendly variants.

mcp-adapter

Guest component template that:

• Exports greentic:component/node@0.6.0 and imports wasix:mcp@25.06.18.
• Accepts JSON payloads of {operation?, tool?, arguments?}:
  • Defaults to list when no tool is provided; defaults to call when a tool is present.
  • Maps list → list-tools, call → call-tool(tool, arguments).
  • Supports shorthand tool calls where runtime operation is a tool id (for example get_weather) and payload is passed as arguments.
• Returns {ok: true, result: ...} envelopes with content/structured-content/meta and lightweight cards/messages for text/image/audio/resource(-link) blocks; elicitations surface as {ok: true, elicitation: ...}.
• Errors use {ok: false, error { code, message, status, tool, protocol, details }} with codes MCP_TOOL_ERROR, MCP_ROUTER_ERROR, or MCP_CONFIG_ERROR.
• Designed to be composed at pack-build time with a router component; the final merged artifact is the component flows should reference.
• See crates/mcp-adapter/README.md for the detailed payload/response contract and composition notes.

greentic-types

Pulled from crates.io; provides TenantCtx, identifiers, and supporting types for multi-tenant flows.

Schema ownership

MCP node configuration schemas ship with the Wasm component that implements the tool. Each component is responsible for returning a describe-json payload (matching greentic:component@1.0.0) that includes its schema/defaults. This repository only bridges the runtime protocol and does not try to duplicate per-tool JSON schemas.

Development

rustup target add wasm32-wasip2
cargo fmt
cargo clippy --all-targets -- -D warnings
cargo test
RUN_ONLINE_TESTS=1 cargo test -p greentic-mcp-exec --test online_weather

The online weather integration test is skipped unless RUN_ONLINE_TESTS=1 is set.

For faster local MCP runs, prefer the release build and enable the Wasmtime cache:

cargo run -p greentic-mcp-exec --release -- router --router /path/to/component.wasm --list-tools

cat > /tmp/wasmtime-cache.toml <<'EOF'
[cache]
enabled = true
directory = "/tmp/wasmtime-cache"
EOF

WASMTIME_CACHE_CONFIG=/tmp/wasmtime-cache.toml \
cargo run -p greentic-mcp-exec --release -- router --router /path/to/component.wasm --list-tools

Local checks

Run ci/local_check.sh before pushing to mirror the CI matrix locally. Helpful toggles:

• LOCAL_CHECK_ONLINE=1 – enable the networked weather test.
• LOCAL_CHECK_STRICT=1 – treat skipped optional steps/tools as failures.
• LOCAL_CHECK_VERBOSE=1 – echo each command.

The script will install a lightweight pre-push hook (if one is not already present) so future pushes automatically run the same checks.

Protocol revisions

The client-side protocol helpers understand multiple MCP protocol revisions. ProtocolRevision defaults to 2025-06-18; configs may optionally set protocol_revision (e.g., "2025-03-26") per server. When unspecified, the latest revision is used while keeping message shapes compatible with older servers.

Structured tool output is carried through as-is: outputSchema is preserved on tools, and tool call results may include structuredContent alongside plain content for richer responses.

Design note: MCP transport (HTTP/JSON-RPC, protocol headers, batching, OAuth token injection) is handled in other Greentic components. This crate only models MCP message shapes and executes tools locally via WIT/wasm host calls.

Releases & Publishing

• Versions are taken directly from each crate's Cargo.toml.
• When a commit lands on master, any crate whose manifest version changed gets a Git tag <crate>-v<version> pushed automatically.
• The publish workflow then runs, linting and testing before calling katyo/publish-crates@v2 to publish updated crates to crates.io.
• Publishing is idempotent; if the specified version already exists, the workflow exits successfully without pushing anything new.

MCP adapter publishing

• greentic-mcp builds and publishes the MCP adapter for wasix:mcp@25.06.18 to GHCR:
  • ghcr.io/greenticai/greentic-mcp-adapter:25.06.18-v<adapter_version>
  • ghcr.io/greenticai/greentic-mcp-adapter:25.06.18-stable (moving pointer)
• The pushed artifact is mcp_adapter_25_06_18.component.wasm, implementing greentic:component/node@0.6.0 and importing wasix:mcp@25.06.18.
• See .github/workflows/publish-mcp-adapter.yml and scripts/build_adapter.sh for the build/publish steps.

Roadmap

• Implement OCI and Warg resolvers, including signature verification.
• Publish spec docs and add end-to-end examples powered by real tool WASMs.

Dev builds

Every Dev Publish run on develop creates a GitHub prerelease tagged v1.2.<run-id> carrying prebuilt greentic-mcp-dev archives, which is what gtc install --channel dev installs. The binary inside reports that same 1.2.<run-id> from --version, so any dev binary can be traced back to the release and the CI run that built it.

License

Dual-licensed under either MIT or Apache-2.0. See LICENSE-MIT and LICENSE-APACHE once added to the repository.