Vue 3 + TypeScript + Vite

This template should help get you started developing with Vue 3 and TypeScript in Vite. The template uses Vue 3 <script setup> SFCs, check out the script setup docs to learn more.

Learn more about the recommended Project Setup and IDE Support in the Vue Docs TypeScript Guide.

Run metadata

Pass metadata to useChatService().initialize():

metadata: {
  mcp__assessmentId: assessmentId,
  mcp__filter: { active: true },
}
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The widget sends mcp__ metadata as AG-UI context on every run. It uses JSON.stringify for every value, including strings, because AG-UI context values must be strings. Values that cannot be serialized reject the send. Reinitializing the same thread replaces its metadata; omitting metadata clears it.

Chat-service forwards keys starting with the case-sensitive mcp__ prefix to every configured MCP server in tools/call.params._meta. It removes the prefix once and decodes the JSON value, preserving strings, numbers, booleans, objects, arrays, and null. No metadata enters the model prompt or tool schema. Unprefixed fields are ignored.

Direct AG-UI clients must use the same encoding: for example, { description: "mcp__assessmentId", value: JSON.stringify(assessmentId) }. The string "123" stays a string; the number 123 stays a number.

Chat-service rejects MCP metadata that exceeds these limits:

• 16 fields.
• 64 characters per stripped name: ASCII letters, digits, _, -, and ., starting and ending with a letter or digit. progressToken is reserved.
• 4,096 UTF-8 bytes per JSON-encoded value.
• 16,384 bytes for the serialized JSON metadata object, including escaping.

Invalid JSON, duplicate names, and missing AG-UI values are also rejected with HTTP 422 before a run starts. JSON null is a valid value. Domain validation and access checks belong to the receiving MCP server; forwarding alone does not restrict retrieval.

This replaces the former metadata-to-prompt behavior. Existing unprefixed fields such as assessmentId no longer reach the model. Migrate callers to mcp__ when their receiving tools can consume and enforce the metadata.