deepseek-harness/packages/workflow/tool-workflow

@deepseek-ai/dsh-tool-workflow

The model-facing workflow tool: run a JavaScript orchestration script that fans out subagents, and return the script's final value. This package owns schema and lifecycle shaping over ctx.workflows; script parsing, execution, caps, and cancellation live behind the seam, while the consumer retains ownership of the parent-facing schema and result envelope.

What the model sees

Three parameters: meta (required identity data: name, description, and optional progress annotations), script (required plain JavaScript body — no export const meta statement; the tool description carries the complete authoring contract), and args (optional JSON object exposed to the script as the args global; wrap a bare list in a field so the wire schema stays honest). The plugin also contributes a tool:<toolName> system-prompt section carrying the usage policy — use the tool only on an explicit user ask for a workflow / large orchestration; prefer plain subagent calls for one or two delegations — per the convention that tool guidance ships with the tool plugin, never in the deployment persona.

Lifecycle

Collection is SYNCHRONOUS this cut (like dsh-tool-subagent): execute starts a run and awaits run.result inside a try/finally that always disposes the run, so the script and its children reach quiescence on every path. exec.signal is bridged to run.cancel() (including the already-aborted-before-start case). A non-completed stop reason maps to an isError result reporting the reason — never partial output as success; a parse/meta failure thrown synchronously by start() becomes an isError the model can correct from. The completed result renders the meta name, the agent count, and the return value as JSON, truncated at maxResultChars with an explicit notice.

Render intent

Decided up front (per the render-intent RFC): a generic card titled workflow: <meta.name>, read directly from args.meta.name (presentation is a pure function of args and does not ask the engine to parse); the script text rides as rawInput. The result keeps the generic card.

Config

Key	Default	Meaning
toolName	workflow	The model-facing tool name to register.
maxResultChars	50000	Rendered-result ceiling; longer JSON is truncated with a notice.

Model Experience

System prompt

What the model sees: Every parent request in this plugin's registration scope receives the workflow guidance below. A scoped tool restriction can hide the schema without removing this independently registered guidance.

Token effect: Small fixed guidance cost per request while the plugin is active.

Workflow guidance

Use the <toolName> tool ONLY when the user explicitly asks for a workflow or for large multi-agent orchestration: you write a JavaScript script (the tool description documents the exact format) that fans work out across many subagents with phases and structured results. For one or two delegations, prefer plain subagent calls.

Tool schema

What the model sees: When visible, the generated default workflow schema carries the complete JavaScript hook and metadata contract; toolName can rename the definition, and the model submits script, metadata, and optional args.

Token effect: Substantial fixed schema cost on each request where the tool is visible.

Tool-call history and result

What the model sees: The full model-written script, metadata, and args remain in the assistant tool call. Success is exactly workflow "<name>" completed (<count> agent<optional-s>)., newline, Return value:, newline, and pretty-printed data-dependent JSON; a cap adds … [truncated: <omitted> more characters] on a new line. Failures are exactly Error: workflow run was cancelled, optionally suffixed (<error>), Error: workflow run failed: <error-or-unknown error>, or defensively Error: workflow run ended abnormally (<reason>); a call without an owning agent becomes Error: workflow tool requires a calling agent (exec.agent was undefined). Intermediate child messages are omitted.

Token effect: Call tokens can be large and remain until compaction. Result rendering is capped by maxResultChars; child-model tokens are separate from the parent's retained context.

Known Limitations and Deferred Work

• The parent turn blocks until the whole workflow settles — there is no background start/poll surface, and cancellation discards partial output as an error.
• args must be an object and the result is bounded text — callers wrap top-level arrays/scalars in a field, and JSON beyond maxResultChars is truncated rather than stored behind a retrieval handle.
• Workflow policy is fixed per tool registration — provider selection, caps, and tool name are deployment config, not model-call arguments.