# Evidence MCP adapter (`execute_capture_plan`) Runtime for the optional **observe\*** step. Writes capture artifacts only — **never** `manifest.jsonl`, never judges L6. ## `DESIGN_PLAYBOOK_RUN_ROOT` | Setting | Meaning | | --- | --- | | Unset | Artifact paths resolve under the **MCP process cwd** | | `"."` (default in package `.mcp.json`) | Same — relative to process cwd, **not** the chat workspace root | | Absolute path | Preferred for cross-repo dogfood: set to the run root (e.g. `D:/…/nmg_bup_h5/.scratch/playbook-smoke/`) so `evidence/L6.*.png` lands next to `manifest.jsonl` | Relative values are resolved with `Path(value).resolve()` at process start semantics (cwd-relative). If captures appear under the plugin monorepo instead of the host run, check cwd and this env — the tool also returns **`written_path`** (absolute) so mis-roots are obvious without a filesystem search. Example (host run): ```json "env": { "DESIGN_PLAYBOOK_RUN_ROOT": "D:/code_space/app/.scratch/my-run" } ``` Plugin auto-load: [`../.mcp.json`](../.mcp.json) (under `packages/design-playbook/`). Codex / manual: sibling [`mcp.example.toml`](../../../design-playbook-evidence/mcp.example.toml). ## Return shape `artifact` (run-root-relative) · `observed_state` (from page `data-state`, else `unknown`) · `result` · `error` · **`written_path`** (absolute). Orchestrator bind rules (verbatim `observed_state`, per-capture append, mirror surface notes): `skills/design-playbook/SKILL.md` step 8. ## Mirror pages and `data-state` When capture uses a semantic mirror (not the live Fill host), set a root marker the provider can read: ```html … ``` `observed_state` comes only from that probe (else `unknown`). Do not overwrite it in the manifest with the request's `state` field.