Nova Cast

Create Component

create_component

Validates, renders and saves a React or HTML component immediately to the right of focus. Success requires browser paint acknowledgement.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "operationID": "<operationID>",
      "expectedRevision": "<expectedRevision>",
      "title": "<title>",
      "format": "<format>",
      "source": "<source>",
      "controlToken": "<controlToken>"
    },
    "name": "create_component"
  }
}

Input Schema

Name	Required	Description
`data`	No
`state`	No
`title`	Yes
`format`	Yes
`source`	Yes	React TSX or full HTML. Use a sized nova-video element: YouTube/Vimeo embed URLs play inline, other service URLs are unsupported; do not create launch buttons or placeholders; see /agent media guidance. Arbitrary nested frames stay blocked. Do not author clickable links or external-navigation buttons; keep interactions within the canvas and share external URLs in the agent conversation.
`operationID`	Yes
`controlToken`	Yes
`expectedRevision`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedSep 29, 2026

TDQS

C2.9/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations declare openWorldHint=true and destructiveHint=false; the description adds a real behavioral trait in 'Success requires browser paint acknowledgement', implying latency and possible failure after mutation. It does not disclose the optimistic-concurrency semantics implied by expectedRevision, nor why an operationID/controlToken is mandatory.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two short, front-loaded sentences with no filler; the mutation and its completion condition come first. Brevity is a virtue here, though it contributes to the param gaps rather than resolving them.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An 8-parameter, 6-required mutation tool with nested objects, no output schema, 13% schema coverage, and CAS-style tokens needs far more explanation than two sentences. The description never addresses the required bookkeeping parameters an agent must supply to succeed.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is only 13% (source is the sole documented property), so the description must compensate. It hints at format ('React or HTML') and placement, but leaves six required parameters — operationID, controlToken, expectedRevision, title, data, state — entirely unexplained and omits the concurrency meaning of expectedRevision.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States specific verbs (validates, renders, saves) plus the resource (React or HTML component) and a placement rule ('immediately to the right of focus'). It is distinguishable from queue_component/update_component in spirit, but never names a sibling to sharpen the distinction.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No when-to-use guidance versus the many overlapping siblings (queue_component, update_component, prepare_draft). No prerequisites stated despite six required parameters including controlToken and expectedRevision.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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