Probative

Probative is an evidence-grounded, multi-agent product discovery toolkit. It takes documents, research and delivery history and produces discovery artifacts in which every claim either cites the source it came from or is labelled a hypothesis with a test attached.

Status: in development. Phases are tracked in PHASES.md. Nothing beyond the foundation (PB0) is built yet — see docs/GETTING-STARTED.md for what v0.1 will do.

Install

uv tool install probative      # or: pipx install probative

Or run it once with nothing to undo:

uvx probative --version

Use it as a Claude plugin

In Claude Code (needs uv on the machine):

/plugin install probative --marketplace vedm1/probative
/probative:setup

/probative:setup runs doctor, shows what the server sees, and tells you the one thing that is missing. The API key is entered with /plugin configure probative@probative (Claude Code's own prompt for a sensitive option) or exported as ANTHROPIC_API_KEY before you start Claude; it is never typed into the chat. Then /probative:critique path/to/prd.pdf. /probative:doctor re-checks the configuration at any time.

The plugin runs uvx --from 'probative[mcp]' probative mcp, so it works once a release is on PyPI; until then use the MCP entry below. Whether Cowork loads this plugin is unverified.

Use it from Claude (MCP)

probative mcp serves critique and doctor (a read-only configuration check) to any MCP client over stdio. It needs the extra:

pip install 'probative[mcp]'

Claude Desktop / Claude Code server entry:

{
  "mcpServers": {
    "probative": {
      "command": "probative",
      "args": ["mcp"],
      "env": {
        "ANTHROPIC_API_KEY": "<your key>",
        "PROBATIVE_MCP_ROOTS": "/path/to/your/specs"
      }
    }
  }
}

The tool reads only inside PROBATIVE_MCP_ROOTS (default: the server's working directory) and writes reports to <first root>/probative-reports/. A run takes 30 to 65 seconds; see OI28 in PROBATIVE_BUILD_PLAN.md for the client-timeout caveat.

Develop

Requires uv and Python 3.12+.

git clone https://github.com/vedm1/probative.git
cd probative
uv sync --all-groups

uv run probative --version
uv run pytest              # passes with no LLM credentials in the environment
uv run ruff check
uv run ruff format --check
uv run mypy src

Copy .env.example to .env and set a provider key if you want to exercise the LLM adapter locally. The default test suite never needs one — see CLAUDE.md § Tests run without an API key.

Why "probative"

Probative is the legal standard for whether evidence actually tends to prove a fact. That's the whole point of this project: every claim in every artifact traces to a line in a document you gave it, or it's marked a hypothesis with a test attached. No number is ever generated by a model — every numeric field is computed by a registered, unit-tested function.

Learn more

• docs/GETTING-STARTED.md — what using it looks like
• docs/DESIGN.md — the full design and the invariants it enforces
• docs/SCENARIOS.md — the same journeys as acceptance tests
• PHASES.md — what's built and what's coming
• CONTRIBUTING.md — adding a critic is a rubric file and one method

The method comes from Dan Olsen's The Lean Product Playbook. Probative implements it; it doesn't replace understanding it.

License

Apache-2.0