> ## Documentation Index
> Fetch the complete documentation index at: https://arizeai-433a7140.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Create a span note

> Add a note annotation to a span. By default each call appends a new note with an auto-generated UUIDv4 identifier, so multiple notes accumulate on the same span. Callers may supply a non-empty `identifier` to upsert on (span_id, name='note', identifier) — repeated calls with the same identifier overwrite the existing note, matching the semantics of structured annotations.



## OpenAPI

````yaml post /v1/span_notes
openapi: 3.1.0
info:
  title: Arize-Phoenix REST API
  description: Schema for Arize-Phoenix REST API
  version: '1.0'
servers: []
security: []
paths:
  /v1/span_notes:
    post:
      tags:
        - spans
      summary: Create a span note
      description: >-
        Add a note annotation to a span. By default each call appends a new note
        with an auto-generated UUIDv4 identifier, so multiple notes accumulate
        on the same span. Callers may supply a non-empty `identifier` to upsert
        on (span_id, name='note', identifier) — repeated calls with the same
        identifier overwrite the existing note, matching the semantics of
        structured annotations.
      operationId: createSpanNote
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CreateSpanNoteRequestBody'
        required: true
      responses:
        '200':
          description: Span note created successfully
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/CreateSpanNoteResponseBody'
        '403':
          description: Forbidden
          content:
            text/plain:
              schema:
                type: string
        '404':
          content:
            text/plain:
              schema:
                type: string
          description: Span not found
        '422':
          description: Validation Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HTTPValidationError'
components:
  schemas:
    CreateSpanNoteRequestBody:
      properties:
        data:
          $ref: '#/components/schemas/SpanNoteData'
      type: object
      required:
        - data
      title: CreateSpanNoteRequestBody
    CreateSpanNoteResponseBody:
      properties:
        data:
          $ref: '#/components/schemas/InsertedSpanAnnotation'
      type: object
      required:
        - data
      title: CreateSpanNoteResponseBody
    HTTPValidationError:
      properties:
        detail:
          items:
            $ref: '#/components/schemas/ValidationError'
          type: array
          title: Detail
      type: object
      title: HTTPValidationError
    SpanNoteData:
      properties:
        span_id:
          type: string
          minLength: 1
          title: Span Id
          description: OpenTelemetry Span ID (hex format w/o 0x prefix)
        note:
          type: string
          minLength: 1
          title: Note
          description: The note text to add to the span
        identifier:
          type: string
          title: Identifier
          description: >-
            Optional caller-supplied identifier. When non-empty, the note is
            upserted on (span_id, name='note', identifier) — repeated calls with
            the same identifier overwrite the existing note. When omitted or
            empty, the server stamps a unique 'px-span-note:<uuid>' identifier
            so each call appends a new note.
          default: ''
      type: object
      required:
        - span_id
        - note
      title: SpanNoteData
    InsertedSpanAnnotation:
      properties:
        id:
          type: string
          title: Id
          description: The ID of the inserted span annotation
      type: object
      required:
        - id
      title: InsertedSpanAnnotation
    ValidationError:
      properties:
        loc:
          items:
            anyOf:
              - type: string
              - type: integer
          type: array
          title: Location
        msg:
          type: string
          title: Message
        type:
          type: string
          title: Error Type
        input:
          title: Input
        ctx:
          type: object
          title: Context
      type: object
      required:
        - loc
        - msg
        - type
      title: ValidationError

````