Agent Builder

When to use

Invoke this skill when the user asks you to:

• Create a new specialised agent (e.g., "build me a daily standup digester").
• Wire a schedule, webhook, or app event to an agent so it fires autonomously.
• Attach a skill or MCP server to an agent you (or the user) own.
• Request a missing capability before performing a gated action.

Do NOT invoke this skill for:

• Editing the system prompt of an already-published agent — that requires forking; the UI handles it.
• Publishing an agent to the marketplace. Publishing is a UI-only action that flips is_published=True after a human review. There is no publish_agent tool.

Hard rules — read before any tool call

1. Depth-1 cap. You can create child agents and attach schedules to them, but those children cannot themselves spawn grandchildren. The attach_schedule tool rejects depth-2 attempts with code depth_exceeded. The DB also enforces depth IN (0, 1) as a second line of defence.
2. Drafts only. Every agent and automation you create starts in DRAFT state:
   • MarketplaceAgent.is_published=False — invisible in the public marketplace.
   • AutomationDefinition.is_active=False — never fires. The user must enable both in the UI before anything goes live.
3. Positive-list inheritance. A child automation's contract MAY only carry scopes from this list: tools.execute, read_file, write_file, bash_exec, web_fetch, web_search, send_message, app.invoke, plus any mcp.* prefix. The non-inheritable scopes you can NOT propagate include marketplace.author and automations.write — attach_schedule rejects child contracts that contain them.
4. Budget rollup. A child automation's max_spend_per_run_usd must be <= the parent's. Daily spend is debited from BOTH the child's daily counter AND every ancestor in the parent chain — if any counter would go negative the run is paused with paused_reason='parent_budget_exhausted'. You cannot use a child to escape a parent's daily cap.

The six tools

create_agent(name, description, system_prompt, model?, tool_allowlist?)

Draft a new MarketplaceAgent row. Returns {agent_id, slug, draft_url, is_published: false}. The row is owned by the calling user and stamped with created_by_automation_id pointing back to your automation, so the dispatcher can walk the provenance chain later.

Required scope: marketplace.author.

update_agent(agent_id, patch)

Patch whitelisted draft fields. Rejects:

• Published rows (is_published=True) — fork via the UI instead.
• Built-in or system rows.
• Any agent the calling user doesn't own.
• The is_published, is_builtin, is_system, id, slug, pricing_type, created_by_* fields — these are server-managed.

assign_skill(agent_id, skill_id)

Insert an AgentSkillAssignment row linking a skill to your agent. Idempotent on the (agent_id, skill_id, user_id) unique constraint — re-running with the same pair is a no-op.

assign_mcp(agent_id, mcp_config_id, scopes?)

Insert an AgentMcpAssignment row linking a user-installed MCP server to your agent. The scopes arg is recorded for audit; the actual mcp.* scope enforcement happens at call time via the automation contract.

attach_schedule(agent_id, trigger, prompt_template, contract, delivery_targets?, workspace_scope?, max_compute_tier?)

Create a child AutomationDefinition that runs the agent on a trigger.

• trigger is {kind, config} where kind ∈ {cron, webhook, app_invocation, manual}.
• prompt_template is the body sent to the agent on each run. It can reference event payload fields with {key} interpolation.
• contract is the runtime contract — see "positive-list inheritance" and "budget rollup" above. The tool runs the inheritance validator before insert; failures surface as contract inheritance violation: <code>: <reason>.
• delivery_targets (optional) is a list of CommunicationDestination UUIDs. Each must be owned by the calling user.
• workspace_scope defaults to user_automation_workspace. The per-user ~automations~ workspace project is lazy-created the first time a user_automation_workspace automation actually fires — there is nothing for you to provision.
• max_compute_tier defaults to 0 (no pod). Bump to 1 for ephemeral pods or 2 for persistent environments — but only if the parent automation's contract allows.

The new automation is created with is_active=False. The user must flip it on in the UI before it starts firing. Required scope: automations.write.

request_grant(resource, capability)

Register an approval card asking the user to grant a capability the run doesn't currently have. Returns {approval_id} immediately. Do NOT block on the response inside the tool — the agent loop must checkpoint on the approval id and let the dispatcher resume the run after the user responds (non-blocking HITL pattern).

resource is {kind, id}; capability is a dotted scope string (e.g., mcp.linear.read).

Recommended flow

1. create_agent to draft the agent row.
2. assign_skill / assign_mcp to attach the dependencies the agent will need at runtime.
3. update_agent to refine the system prompt, tool allowlist, or metadata as you learn more about what the user wants.
4. attach_schedule to wire a trigger + contract + delivery targets.
5. Tell the user where to find the draft (draft_url from create_agent) and remind them they need to publish the agent + enable the automation from the UI before it goes live.

Common failure modes

• depth_exceeded — you're already running inside a child automation. Refactor the parent automation to spawn what you need directly.
• scope_not_inheritable — the child contract carries marketplace.author, automations.write, or another non-positive-list scope. Drop it from the child contract.
• per_run_cap_exceeded — the child's max_spend_per_run_usd is larger than the parent's. Cap it at or below the parent's value.
• daily_cap_exceeded — the child's daily cap exceeds the parent's remaining daily budget at attach time. Lower the child cap or wait for the parent's daily counter to reset.

Source: TesslateAI/OpenSail — distributed by TomeVault.