git:20260318.233330d to git:20260616.53dc97b

# Tools - Agent Instructions

## New Non-Skill Tools Are Strongly Discouraged

Skills are the preferred approach for adding new capabilities — they are progressively disclosed into context, more portable, and can be iterated on independently. New non-skill tool registrations (`class ... implements Tool` + `registerTool()`) carry additional costs:

1. **Context overhead** — Each registered tool adds to the system prompt and increases token usage for every conversation.

2. **Maintenance burden** — Tools require ongoing maintenance, testing, and security review.

## What To Do Instead

Instead of creating a new tool, consider:

1. **Create a skill**

2. **Use existing tools** - Many capabilities can be achieved by combining existing tools (bash, file operations, network tools) with skill instructions.

3. **External CLI tools** - If you need new functionality, consider whether it can be exposed as a CLI tool that the assistant can invoke via bash.

## Approved Exception: Credential Execution Service (CES) Tools

The following three CES tools are approved exceptions that justify tool registrations over skills:

| Tool | Purpose |

| ---------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------- |

| `run_authenticated_command` | Execute a shell command with credential env vars injected by CES across a hard process boundary |

| `make_authenticated_request` | Execute an authenticated HTTP request with credentials injected by CES; returns response body and status only |

| `manage_secure_command_tool` | Register and manage secure command tool bundles in the CES toolstore; handles bundle lifecycle (registration, unregistration) for manifest-driven commands |

These tools exist as `class ... implements Tool` registrations because:

- They enforce hard process-boundary isolation - credential values are materialized only inside the CES process (`credential-executor/` package), never in the assistant process

- Skills run inside the assistant process and cannot provide this isolation guarantee

- The tools are thin RPC stubs; actual credential materialization and execution logic lives in the separate `credential-executor/` package

**Key constraints**:

- CES is a **separate package and image** - no direct source imports from `assistant/` to `credential-executor/` or vice versa

- **Grants and audit logs are CES-owned** durable state - the assistant never reads or writes CES grant or audit tables directly

- `host_bash` is **outside the strong CES secrecy guarantee** - it does not enforce credential isolation

- Secure generic authenticated HTTP **must not** run through `run_authenticated_command` - use `make_authenticated_request` instead, which enforces domain validation and produces structured audit logs

- Managed rollout requires a **third runtime image** (alongside assistant and gateway) and `vembda` pod-template changes

See [`assistant/docs/credential-execution-service.md`](../../docs/credential-execution-service.md) for the full ADR.

## If You Have Approval

1. The pre-commit hook will block your commit by default

2. Use `git commit --no-verify` to bypass the hook

3. Include the approval context in your PR description

## Questions?