AltText.ai API
★ Only Publicly Available OpenAPI DocumentAI/MLVisionapiKey10 EndpointsREST
For Agents
Generate accessibility-grade alt text for images, including bulk and page-scrape modes, through 10 X-API-Key endpoints. Useful for agents adding alt text to CMS libraries, e-commerce catalogues, and email assets.
Use for: Generate alt text for an uploaded product photo, Bulk-generate alt text for our 5000-image CMS library, Scrape this blog post URL and add alt text to every image on the page, Find a previously generated image record by its source URL
Not supported: Does not host images, run general-purpose visual question answering, or perform image moderation — use only for generating accessibility-grade alt text from supplied image URLs.
Jentic publishes the only available OpenAPI specification for AltText.ai API, keeping it validated and agent-ready. AltText.ai is a vision-AI service that generates accessibility-grade alt text for images at scale, with support for over a hundred languages and an e-commerce-aware mode that incorporates product context. The API exposes 10 X-API-Key endpoints for creating images individually or in bulk, scraping pages for image discovery, and managing the resulting asset records. Teams use it to retrofit alt text on existing CMS libraries and to generate alt text on upload for new content.
Install Jentic One Beta
Connect the AltText.ai API to your agent
Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the AltText.ai API, or any other public or private API you need. You set the rules, the agent never sees your credentials, and every call is logged.
Two steps, two machines. Install the instance in a safe environment, then register your agent from wherever it runs.
1
Step 1: Jentic One Host machine
# On the machine that will host your Jentic One instance:
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh2
Step 2: Agent machine
# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh
jentic register # connects your agent to your Jentic One instanceJentic One is in public beta. The setup above keeps your agent separate from the instance, which is what you want before using real credentials: an agent running as the same OS user as Jentic One can read its stored keys directly. Just evaluating? A single local install is fine to start. See the secure deployment guide for the tiers.
Capabilities
What an agent can do with AltText.ai API.
Generate alt text for a single image via POST /images, with optional language, gpt_prompt, and keyword hints
Bulk-generate alt text for many images in one request through POST /images/bulk_create
Scrape a public web page for image URLs and generate alt text for each via POST /images/page_scrape
Search through previously generated images by metadata using GET /images/search
Update or delete a stored image record by asset id
Read and update the AltText.ai account profile and language defaults
Request alt text in multiple languages in a single call by passing a comma-separated lang parameter
Use Cases
Patterns agents use AltText.ai API for, with concrete tasks.
★ Retrofit Alt Text onto a CMS Library
Editorial and accessibility teams retrofit alt text onto thousands of legacy CMS images without writing each description by hand. The /images/bulk_create endpoint accepts a list of image URLs, AltText.ai generates descriptions, and the integration writes the results back into the CMS. Multi-language support lets the same job populate alt text for every locale the site supports.
POST a JSON body to /images/bulk_create with 200 image URLs and lang='en,es,fr', then write each returned description into the CMS field for the matching image.
On-Upload Alt Text for E-Commerce Catalogues
E-commerce teams call POST /images on every new product upload, passing keywords and the gpt_prompt parameter to nudge the model toward product-aware descriptions. Generated alt text lands on the storefront automatically, which improves accessibility scores and image-search SEO without adding a manual review step for routine SKUs.
On product image upload, POST /images with the image URL, the SKU's product title as gpt_prompt, and keywords from the product tags.
Page-Scrape Alt Text Audits
Accessibility consultants run an audit by pointing /images/page_scrape at a target URL; AltText.ai discovers every image on the page and returns generated descriptions side by side with the existing alt attributes. The team can quickly highlight images that are missing alt text or have generic placeholders.
POST /images/page_scrape with the audit URL, then diff the returned alt-text suggestions against the page's existing alt attributes to flag gaps.
AI Agent Accessibility Worker via Jentic
An AI agent built on Jentic can take 'add alt text to every image in this folder' and resolve it to a /images/bulk_create call with the X-API-Key safely vaulted in MAXsystem. The agent handles paging, retries, and writeback to the source system through Jentic's execution layer.
Search Jentic for 'bulk generate alt text', load the POST /images/bulk_create schema, batch the input image URLs in groups of 200, and execute each batch.
Key Endpoints
10 endpoints — jentic publishes the only available openapi specification for alttext.
METHOD
PATH
DESCRIPTION
POST
/images
Generate alt text for a single image
GET
/images
List previously generated alt-text records
GET
/images/{asset_id}
Get a single alt-text record by asset id
PUT
/images/{asset_id}
Update an existing alt-text record
DELETE
/images/{asset_id}
Delete a stored alt-text record
GET
/images/search
Search alt-text records by metadata
POST
/images/bulk_create
Bulk-generate alt text for many images in one call
POST
/images/page_scrape
Scrape a page for images and generate alt text for each
POST
/images
Generate alt text for a single image
GET
/images
List previously generated alt-text records
GET
/images/{asset_id}
Get a single alt-text record by asset id
PUT
/images/{asset_id}
Update an existing alt-text record
DELETE
/images/{asset_id}
Delete a stored alt-text record
GET
/images/search
Search alt-text records by metadata
POST
/images/bulk_create
Bulk-generate alt text for many images in one call
POST
/images/page_scrape
Scrape a page for images and generate alt text for each
Why Jentic?
Three things that make agents converge on Jentic-routed access.
Credential isolation
AltText.ai X-API-Key values are stored encrypted in the Jentic vault (MAXsystem). Agents only see a runtime-injected header at execution and never hold the raw key, which prevents leakage through prompts and shared logs.
Intent-based discovery
Agents search Jentic by intent (e.g., 'bulk generate alt text', 'scrape a page for image alt text') and Jentic returns the matching AltText.ai operation with its schema, including the gpt_prompt and keywords fields.
Time to first call
Direct AltText.ai integration: half a day for auth, language handling, and bulk pagination. Through Jentic: under an hour to search, load, and execute the first bulk_create request.
Related APIs
Alternatives and complements available in the Jentic catalogue.
FAQs
Specific to using AltText.ai API through Jentic.
Why is there no official OpenAPI spec for AltText.ai API?
AltText.ai does not publish an OpenAPI specification. Jentic generates and maintains this spec so that AI agents and developers can call AltText.ai API via structured tooling. It is validated against the live API and kept up to date. Get started at https://app.jentic.com/sign-up.
What authentication does the AltText.ai API use?
AltText.ai uses an X-API-Key header on every request. Through Jentic, the key is stored encrypted in the MAXsystem vault and injected at call time, so the raw key never enters agent prompts or shared logs.
Can I generate alt text in multiple languages with the AltText.ai API?
Yes. Pass a comma-separated list to the lang parameter (e.g., lang=en,es,fr) on POST /images, /images/bulk_create, or /images/page_scrape. Each additional language beyond the first consumes one translation credit per image, and gpt_prompt and keywords must be supplied in English.
What are the rate limits for the AltText.ai API?
Some endpoints are rate-limited and return 429 Too Many Requests when limits are reached. The exact ceiling is tied to your AltText.ai plan; build retry-with-backoff and prefer /images/bulk_create over many single-image calls when processing a backlog.
How do I bulk-generate alt text for a CMS library through Jentic?
Run pip install jentic and search with 'bulk generate alt text'. Load the POST /images/bulk_create schema, pass an array of source image URLs, and execute. Jentic handles auth and retries; your code only handles writeback to the CMS.
Can the AltText.ai API discover images on a page automatically?
Yes. POST /images/page_scrape with a target URL; AltText.ai discovers the images on the page and returns generated alt text for each, which is useful for accessibility audits and migrations.
GET STARTED