Web Capability Compiler (WCC)

Compile existing websites into reusable, typed capabilities for MCP agents.

WCC is not another browser-use agent. It is a compilation, binding, and caching layer that sits between an existing website and an external AI agent.

Browser agents typically re-interpret low-level UI elements on every task, which costs tokens, reduces repeatability, and ties workflows to transient DOM detail. WCC inspects a page once, compiles the observable controls into a small set of semantic, typed, low-risk capability templates, binds compatible templates to the current session, and lets an MCP client execute them through a stable interface. On repeated use it tries to bind a persisted template before recompiling, so the agent can skip low-level DOM interpretation entirely.

The headline metric is token reduction on repeated tasks, not task success rate.

Status

MVP v0.1 is under construction against spec v0.2.1. Phases 0–5 of 7 are complete, and it runs as an MCP server today. The loop closes: WCC reads a live document into a snapshot, builds an Agent Page IR, compiles typed search, filter, and navigation capabilities with evidence and a deterministic risk classification, persists them as reusable templates, binds a stored template on a later session without recompiling, and executes one — validating arguments against its schema, re-resolving every target, re-checking risk against the page in front of it, running the plan one allowlisted action at a time, and verifying afterwards that the intended effect actually happened.

All of that is reachable from any MCP client over stdio, through six stable tools. What remains is Phase 6 (optional LLM enrichment, which the system works without) and Phase 7 (the token-reduction benchmark).

Three properties are worth stating plainly, because they are what the design is for: only low-risk capabilities ever execute; an execution is reported as successful only when its effect was observed; and no selector, screenshot, or coordinate crosses the MCP boundary in either direction — a test asserts the last one by searching every tool response for the fixtures' own selectors.

See docs/progress.md for the phase log, which records the reasoning behind each decision and the defects found along the way.

Related MCP server: ApiTap

Quickstart

No clone required. uv and Python 3.12+ are the only prerequisites.

# Install the Chromium build the driver uses (once)
uvx --from git+https://github.com/Maaa2005/web-capability-compiler.git wcc install-browser

# Check the machine before pointing a client at it
uvx --from git+https://github.com/Maaa2005/web-capability-compiler.git wcc doctor

# Run the MCP server over stdio
uvx --from git+https://github.com/Maaa2005/web-capability-compiler.git wcc serve

Connecting an MCP client

Claude Code:

claude mcp add wcc -- uvx --from git+https://github.com/Maaa2005/web-capability-compiler.git wcc serve

Claude Desktop (claude_desktop_config.json) or any client that takes a command:

{
  "mcpServers": {
    "wcc": {
      "command": "uvx",
      "args": [
        "--from",
        "git+https://github.com/Maaa2005/web-capability-compiler.git",
        "wcc",
        "serve"
      ]
    }
  }
}

Then ask the agent to open a page and inspect it. It will get back a list of typed capabilities rather than a DOM.

The six tools

Generated capabilities are returned as typed data, not registered as MCP tools — so the client's tool list never changes as the agent browses.

Configuration

Set by whoever launches the server, never by an agent over the wire.

Operating it

uv run wcc diagnostics                        # sanitized counts and environment checks
uv run wcc export --session <id> --output caps.json
uv run wcc import caps.json                   # checked on the way in, re-verified at bind time
uv run wcc clear-data                         # remove all local WCC data

An imported capability is stored, never trusted: it re-resolves its targets and is re-classified for risk against the live page before it can run, exactly as a locally compiled one is.

Development

uv sync
uv run wcc --help
./scripts/test.sh

Scope of MVP v0.1

Supported capability categories are search, filter, and navigate. Only low risk capabilities are executable. Purchases, account changes, message sending, and any state-changing form submission are out of scope, as are CAPTCHA bypass, anti-bot evasion, and credential storage.

The full scope, data model, risk model, and benchmark methodology live in docs/spec/WCC_AGENT_IMPLEMENTATION_SPEC_v0.2.1.md, which is the source of truth for implementation.

License

MIT