canonical: https://jentic.com/apis/imagetocaptionai.com/imagetocaptionai # Imagetocaptionai Create Caption API Jentic publishes the only available OpenAPI specification for Create Caption API, keeping it validated and agent-ready. Create Caption API exposes a single endpoint that takes an image and returns a generated caption. The service is positioned as a Zapier-friendly building block for social media managers who want descriptive, on-brand captions for Instagram, LinkedIn, and similar feeds. The API accepts an image reference and returns the caption text in a JSON response. ## For AI agents Generate a social-media-style caption for a supplied image with a single POST request - useful inside content pipelines and scheduled-post agents. ## Scope Does not handle image hosting, post scheduling, or analytics - use for generating a caption from an image only. ## Capabilities - Generate a caption for an image supplied by URL or upload - Drop a caption-generation step into a Zapier or n8n content workflow - Pre-fill caption fields in a social media scheduling tool from a chosen image - Generate alt-text-style descriptions for accessibility audits - Produce baseline captions that a human editor can refine before posting ## Use cases ### Caption Generation in Content Pipelines Marketing teams that schedule social posts from a queue can wire a caption-generation step in front of the scheduler. The image goes to /create-caption, the returned text is stored alongside the post, and an editor approves or edits it. This trims the time spent staring at an empty caption field for every queued image. Example prompt: POST /create-caption with the image URL, store the returned caption on the queued post, and route it to the editor for approval. ### Alt-Text for Accessibility Audits Sites with thousands of marketing images often lack alt text. Looping image URLs through /create-caption produces a draft alt-text per image that a content editor can sanity-check, which is faster than writing every description from scratch. Audits that previously took weeks can be cut to days. Example prompt: Iterate over a CMS image list, POST each URL to /create-caption, write the result back to the alt attribute, and flag any image where the response is empty. ### Zapier and n8n Workflows Because the API is a single POST endpoint with no auth scheme declared in the spec, it slots cleanly into low-code workflow tools. Triggers like 'new image in Drive' can call /create-caption and pipe the result into Buffer, Hootsuite, or a Notion log without any glue code. Example prompt: Configure a webhook step that POSTs the new image URL to /create-caption and forwards the returned caption to the next step in the zap. ### Agent-Driven Social Posting An AI agent that drafts and schedules social posts can call this API for the caption sub-step, freeing the model from generating image-aware text without seeing the image. Through Jentic the agent searches by intent and runs the operation, then composes the final post around the returned caption. Example prompt: Search Jentic for 'generate a caption for an image', execute /create-caption with the chosen image, then call the social network's posting API with the returned caption text. ## Key endpoints | Method | Path | Description | | --- | --- | --- | | POST | `/create-caption` | Generate a caption for a supplied image | ## Key resources - **Create Caption** — Generate a caption from an image. ## Why Jentic - **Setup:** Wiring the Create Caption API by hand means posting the image reference to its single endpoint and shaping the request yourself. Through Jentic you install once, import the Create Caption API from the API Directory, and your agent calls it with no key to manage. - **Permission scoping:** The Create Caption API exposes a single caption operation with the image passed in the request body rather than a path resource id, so scope the agent to that one operation it needs. Because you choose the allowed operations, the agent is limited to caption creation. - **Credential handling:** This endpoint has no required credential, so there is nothing to store. If the vendor adds a key later, your own Jentic One instance would store it encrypted and inject it at execution time so it never enters the agent's prompt, logs, or context. - **Discovery method:** Agents search Jentic by intent such as 'generate a caption for an image', and Jentic returns the /create-caption operation with its input schema so the agent passes the image reference correctly on the first try without browsing the reference docs. ## Related APIs - **OpenAI** — OpenAI's vision-capable chat completions can generate captions and alt text directly from images. - **Imagga** — Imagga adds tagging, categorisation, and content moderation that pair well with caption generation. - **Clarifai** — Clarifai offers vision models for tagging, captioning, and custom training. ## FAQ ### Why is there no official OpenAPI spec for Create Caption API? imagetocaption.ai does not publish a public OpenAPI specification. Jentic generates and maintains this spec so that AI agents and developers can call Create Caption API via structured tooling. It is validated against the live API and kept up to date. Get started with Jentic One, the self-hosted execution layer. ### What authentication does the Create Caption API use? The OpenAPI spec declares no security scheme on the /create-caption endpoint. The vendor's hosted product authenticates through their dashboard rather than per-request headers; if they add a key in future, Jentic will store it encrypted in the vault. ### Can I generate captions from an image URL? Yes. POST /create-caption with the image reference and the response contains the generated caption text. The endpoint is designed for one image per call, which fits inside Zapier-style step limits. ### How do I generate a caption through Jentic? Run pip install jentic, search for 'generate a caption for an image', load the /create-caption schema, and execute with the image URL. Jentic returns the caption to the agent for use in the next step of a content workflow. ### What are the rate limits for the Create Caption API? The OpenAPI spec does not list explicit rate limits. Plan for one-image-per-call usage and back off on HTTP 429 responses if running batch jobs over hundreds of images. ### Can I limit what my agent is allowed to do with the Create Caption API? Yes. Because Jentic One is self-hosted and your own rules decide which operations an agent may call, you can scope this agent to the single POST /create-caption operation and nothing else. The API exposes only that one caption-creation operation, with the image passed in the request body rather than as a path resource, so allowing that operation limits the agent to generating captions from images. It cannot reach any other action, since you approve each operation the agent is permitted to run.