tool

Language reference / tool

Meaning and placement

invoke

Tool reference · nika:<path> (closed v0.1 builtin set) OR mcp:<server>/<tool> (requires the slash). The namespace set is CLOSED at v1 (spec/02-verbs.md) — an x-<vendor>: prefix is RESERVED, not valid (engine-specific tools route through mcp: · spec/06-stdlib-contract.md §Namespace ownership).

Property	Declaration
Requirement	Optional in this object
Schema location	`/$defs/invoke/properties/tool`

In the same object: args · workflow Schema source (use the pointer above)

In a source template

Excerpt from templates/agent-loop.nika.yaml, source lines 137–146. This is a fragment, not a runnable workflow.

illustration

      # answer: that gap closes upstream, by binding the goal into the agent.
      has_findings: ${{ size(tasks.execute.output.findings) > 0 }}   # the check crosses as ONE boundary expression · SLOT: your law
    invoke:
      tool: "nika:assert"
      args:
        condition: "${{ with.has_findings }}"
        message: "Agent returned no findings, do not trust an empty run"   # SLOT

outputs:
  findings:

Templates containing this field

Template	Source
`templates/agent-loop.nika.yaml`	Line 140
`templates/api-upload-and-create.nika.yaml`	Line 70
`templates/chain.nika.yaml`	Line 48
`templates/classify-and-route.nika.yaml`	Line 96
`templates/corpus-qa.nika.yaml`	Line 34
`templates/docker-report.nika.yaml`	Line 92
`templates/document-to-fields.nika.yaml`	Line 40
`templates/etl-state.nika.yaml`	Line 72
`templates/fanout.nika.yaml`	Line 88
`templates/gate-and-act.nika.yaml`	Line 53
`templates/human-gated-ship.nika.yaml`	Line 95
`templates/media-asset-pack.nika.yaml`	Line 73
`templates/website-brief.nika.yaml`	Line 52

These are literal key occurrences in the source files, not an execution or conformance claim. How to instantiate a template.

Contract and implementation

This page projects the named specification revision. Check released engine status and the validation workflow before running a file. An optional field is not evidence that every engine supports every value. Canonical identity: language:word:tool. Spec revision: c5ebbb7b862b. How documentation stays connected.

YAML

Language fields

CLI & errors

Data catalogs

Workspace

Documentation system

Tool contracts

Meaning and placement

invoke

In a source template

Templates containing this field

Contract and implementation

​Meaning and placement

​invoke

​In a source template

​Templates containing this field

​Contract and implementation

Meaning and placement

invoke

In a source template

Templates containing this field

Contract and implementation