> ## Documentation Index
> Fetch the complete documentation index at: https://docs.tilt.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Inspect a construction field

> Inspect field metadata, coverage, and distribution.



## OpenAPI

````yaml api-reference/index-construction-preview-openapi.yaml POST /api/v1/catalog/inspect
openapi: 3.1.0
info:
  title: 'Tilt Index Construction API: Design Preview'
  version: 0.4.0-design-preview
  summary: >-
    A restrained public projection of Tilt's existing index construction
    workflow.
  description: |
    A Tilt is a persistent project for one index methodology. Its construction
    rules are the source, evaluated constituent snapshots are the build
    artifacts, and methodology history is version history. This bounded
    repository analogy does not imply branches, forks, merges, or cloning.

    This contract covers rules-based equity construction only. Applying
    construction saves the rules, evaluates them, and commits the complete
    weighted constituent snapshot atomically.
servers:
  - url: https://x.invalid
    description: Non-routable design preview
security:
  - ApiKey: []
tags:
  - name: Tilts
    description: Organization-owned Tilt projects and versions.
  - name: Construction
    description: Apply methodology and read its saved weighted evaluation.
  - name: Catalog
    description: >-
      Discover fields, functions, universes, and classifications used in
      expressions.
  - name: Tickers
    description: Resolve security identifiers to exact Tilt asset IDs.
  - name: Backtests
    description: Backtest a saved Tilt using its configured rebalance behavior.
paths:
  /api/v1/catalog/inspect:
    post:
      tags:
        - Catalog
      summary: Inspect a construction field
      description: >-
        Returns units, coverage, nulls, and distribution percentiles for one
        exact field name.
      operationId: inspectConstructionField
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CatalogInspectRequest'
            example:
              column_name: market_cap
      responses:
        '200':
          description: Field metadata and distribution.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/CatalogInspectResponse'
        '400':
          $ref: '#/components/responses/BadRequest'
        '401':
          $ref: '#/components/responses/Unauthorized'
components:
  schemas:
    CatalogInspectRequest:
      type: object
      additionalProperties: false
      required:
        - column_name
      properties:
        column_name:
          type: string
          minLength: 1
    CatalogInspectResponse:
      type: object
      required:
        - success
        - column_name
        - unit
        - total_securities
        - non_null_count
        - null_count
        - null_percentage
        - percentiles
      properties:
        success:
          type: boolean
        column_name:
          type: string
        unit:
          type:
            - string
            - 'null'
        total_securities:
          type: integer
        non_null_count:
          type: integer
        null_count:
          type: integer
        null_percentage:
          type: string
        percentiles:
          type: object
          properties:
            min:
              type: number
            p10:
              type: number
            p25:
              type: number
            p50:
              type: number
            p75:
              type: number
            p90:
              type: number
            p95:
              type: number
            p99:
              type: number
            max:
              type: number
    Error:
      type: object
      required:
        - error
      properties:
        error:
          type: object
          additionalProperties: false
          required:
            - code
            - message
          properties:
            code:
              type: string
            message:
              type: string
  responses:
    BadRequest:
      description: The request is invalid.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    Unauthorized:
      description: The API key is missing or invalid.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
  securitySchemes:
    ApiKey:
      type: apiKey
      in: header
      name: X-Api-Key

````