# Taruvi App Developer

> Backend work on a Taruvi app: provisioning datatables, Cerbos policies, roles, users, buckets, secrets, analytics queries, or raw SQL via the Taruvi MCP server; and authoring Python function bodies that run in the Taruvi function runtime (`def main(params, user_data, sdk_client)`) for multi-resource cascades, event/cron handlers, public webhooks, and external API calls. Triggers: "create a datatable", "Frictionless schema", "Cerbos policy", "serverless function", "scheduled job", "analytics query", "sdk_client", `manage_function`, `execute_raw_sql`. Skip for Refine frontend work — use `taruvi-refine-providers` instead.

- Skill: `taruvi-ai/taruvi-app-developer` (Agent Skill, multi-file: 25 files)
- Install (CLI): `npx skillmds@latest add taruvi-ai/taruvi-app-developer`
- Raw SKILL.md: https://api.skillmd.com/api/skills/taruvi-ai/taruvi-app-developer/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Web & Frontend
- License: Apache-2.0
- Author: taruvi-ai (https://skillmd.com/u/taruvi-ai)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/taruvi-ai/taruvi-app-developer

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# Taruvi app developer (backend)

Single backend skill for Taruvi. Covers two layers:

- **Control plane (MCP)** — provisioning datatables, policies, roles, buckets, secrets, function metadata, analytics queries, audited raw SQL.
- **Data plane (function runtime)** — Python bodies with signature `def main(params, user_data, sdk_client)` running on Celery workers with a pre-authenticated `sdk_client`.

If the task is wiring React/Refine providers or hooks on the frontend, switch to `taruvi-refine-providers`.

## Decision: function or just MCP provisioning?

Provisioning alone is enough for: schema changes, policy/role/user management, bucket creation, secret management, registering analytics queries, one-shot admin SQL.

You need a **function body** when the task involves any of:

- 2+ resources at runtime (DB + storage, users + DB, etc.)
- Event triggers (`RECORD_CREATE`, `RECORD_UPDATE`, `RECORD_DELETE`, `POST_USER_CREATE`, …)
- Schedule / cron
- External API call with a stored secret
- Long-running work (>30s → `async_mode=True`)
- Public unauthenticated endpoint (`is_public=True`)
- Authorization gate beyond plain Cerbos resource policy
- Function-to-function pipeline

When in doubt, see [`when-not-to-use-functions.md`](references/when-not-to-use-functions.md).

## Workflow

1. Read [`architecture-overview.md`](references/architecture-overview.md) once for the runtime split; for greenfield apps also scaffold an `AGENTS.md` from [`agents-md-template.md`](references/agents-md-template.md).
2. Decide function vs provisioning (above). Before writing function code, read [`function-authoring.md`](references/function-authoring.md) and the relevant section of [`function-sdk-reference.md`](references/function-sdk-reference.md).
3. For MCP work, open [`mcp-tool-quickref.md`](references/mcp-tool-quickref.md) and the task-specific reference below.
4. For destructive ops, follow the destructive-op protocol (below).
5. Verify by re-reading the resource (`get_datatable_schema`, `manage_policies(action="get")`, etc.) and executing functions / analytics queries end-to-end before reporting done.

## Reference index

| Task | Read |
|---|---|
| MCP tool signatures | [`mcp-tool-quickref.md`](references/mcp-tool-quickref.md) |
| Frictionless schema (FKs, indexes, hierarchy, graph) | [`datatable-schema-patterns.md`](references/datatable-schema-patterns.md) |
| Cerbos policy authoring | [`cerbos-policy-cookbook.md`](references/cerbos-policy-cookbook.md) — or `get_ai_docs(category="policies", topic="guide")` |
| Secrets and custom secret types | [`secrets-and-types.md`](references/secrets-and-types.md) |
| Audited raw SQL | [`raw-sql-safety.md`](references/raw-sql-safety.md) |
| Analytics queries (registration + Jinja2 params) | [`analytics-queries.md`](references/analytics-queries.md) |
| Filter operators / query capabilities | [`backend-capabilities.md`](references/backend-capabilities.md) |
| Function runtime contract, modes, triggers | [`function-authoring.md`](references/function-authoring.md) |
| `sdk_client` modules and methods | [`function-sdk-reference.md`](references/function-sdk-reference.md) |
| Event triggers, CEL filters | [`function-events.md`](references/function-events.md) |
| Worked function examples (8 scenarios) | [`function-scenarios.md`](references/function-scenarios.md) |
| Cross-layer worked features | [`feature-workflow-examples.md`](references/feature-workflow-examples.md) |
| Integration pitfalls | [`integration-pitfalls.md`](references/integration-pitfalls.md) |
| Frontend Worker deploy | [`frontend-worker-deploy.md`](references/frontend-worker-deploy.md) |
| Export backend config | [`backend-export.md`](references/backend-export.md) |
| Env var setup | [`env-setup.md`](references/env-setup.md) |

## Non-negotiables

Most of these are wired into the references too — listed here because skipping them causes real bugs.

1. **Trust the MCP tool, not memory.** Tool responses carry the IDs/slugs/status you need next. Don't invent endpoints or method names.
2. **`create_update_schema` drops fields missing from the payload.** Always `get_datatable_schema` first, then send the full preserved field list.
3. **`manage_policies(action="create_update")` replaces — does not merge.** Get the existing policy first, mutate, and send the full body back.
4. **Function signature is exactly `def main(params, user_data, sdk_client):`.** Any deviation → immediate `SandboxError`.
5. **Never re-authenticate `sdk_client`.** It's pre-authenticated. No `client.auth()`, no `client.login()`, no API keys passed in.
6. **Never hardcode secrets.** Use `sdk_client.secrets.get("KEY")`.
7. **Return JSON-serializable values from functions.** `datetime`, `set`, `Decimal`, and custom classes crash on return — convert first.
8. **Tasks >30s need `is_async=True`.** Sync calls time out at 30s and leave UI spinners stuck.
9. **Use `log()`, not `print()`.** `print()` is unstructured stdout and not queryable.
10. **Frontend multi-resource cascades are bugs.** Move them to a function — browser navigation mid-operation leaves the DB inconsistent.

## Destructive-op protocol

Applies to: `delete_datatable` (especially `force=True`), `manage_policies(action="create_update")` on an existing policy, `user_attributes_schema(action="update")`, `manage_secret_types(action="delete")`, `manage_function(action="delete")`, `manage_roles(action="delete")`, and any `execute_raw_sql` containing `DROP`, `TRUNCATE`, destructive `ALTER`, or `DELETE` without `WHERE`.

1. **Plan** — inspect current state (`get_datatable_schema`, `manage_policies(action="get")`, …) and state what will be deleted/replaced and what depends on it.
2. **Validate** — surface the blast radius in plain language ("This will drop `orders` and 3 dependent FKs in `invoices`"). Get explicit user confirmation.
3. **Execute** — only after confirmation. Report the tool's response verbatim.

## Test users — always

After provisioning, create test users so the user can verify the app works:

- **With access control:** one test user per role, named `qa_<role_slug>_<YYYYMMDD>` (e.g., `qa_warehouse_staff_20260422`), strong 12+ char password (mixed case + digit + symbol). Report all usernames and passwords back to the user.
- **No access control:** one default super-admin test user, password reported.
- **Include cleanup guidance:** deactivate/delete the `qa_*` users after validation, or rotate their passwords.

## Verify by executing — always

Before reporting a function or analytics query done:

1. Run `execute_function(function_slug=..., params={...})` or `execute_query(query_slug=..., params={...})` with realistic sample params.
2. Inspect the actual response shape.
3. Confirm any frontend code uses the exact field names and structure returned — fix the frontend if they don't match.

## Drift check

`node scripts/check-versions.js` warns when pinned SDK/provider versions drift from the latest on PyPI/npm.