Unified AI API Tutorial: Keep Model Contracts Explicit

Why I wrote this

When I review a unified AI API, I do not start by counting model names. I start by checking which contracts are explicit, which jobs are asynchronous, and where the application must keep its own validation and review gates. This is the contract-first checklist I use to separate a useful access layer from a misleading “one schema for everything” abstraction.

Direct answer

A useful unified AI API gives your application one access layer without
pretending that every model behaves the same.

Centralizing the account, base URL, authentication pattern, and route discovery
can reduce integration overhead. But image, video, speech, chat, and commerce
tasks still have different parameters, response patterns, and review
requirements. A reliable implementation keeps those contracts explicit.

This guide shows a contract-first workflow using XPLA's documented route
families as the example. The method also applies when you are designing your
own multi-model gateway.

What should a unified AI API actually unify?

The word unified is useful when it describes:

• one account and access layer;
• one base URL;
• one Bearer-token pattern;
• one place to discover current models;
• explicit routes for different task families;
• a consistent place to check current documentation.

It becomes misleading when it implies:

• one universal request body;
• identical model parameters;
• identical synchronous or asynchronous behavior;
• a fixed catalog available to every account;
• guaranteed failover, lower cost, latency, throughput, or uptime.

The safest architecture unifies access while preserving model contracts.

1. Define the application job before choosing a model

Start with the result your user needs:

• What is the input?
• What output must be delivered?
• Is a response needed immediately?
• Can the task run asynchronously?
• Does the task contain private media?
• What rights and retention rules apply?
• What must a human review before the result is used?

This decision should select a route family before it selects a model name.

Application job	XPLA route	Pattern
Discover models available to a token	GET /v1/models	synchronous JSON
Generate or edit an image	POST /v1/images/generations	synchronous for supported contracts
Create a video task	POST /v1/videos	asynchronous
Check a video task	GET /v1/videos/{task_id}	poll by task ID
Retrieve completed video content	GET /v1/videos/{task_id}/content	authenticated content read
Run a chat completion	POST /v1/chat/completions	completion or streaming contract
Generate speech	POST /v1/audio/speech	text-to-speech contract
Search TikTok Shop data	GET /v1/tiktok/shop/search	commerce-data query
Get one TikTok product	GET /v1/tiktok/product	product lookup
Parse an authorized public video	POST /v1/video/parse	public-video analysis

The table is a route-selection aid, not a guarantee that every model is enabled
for every account. Check the current documentation before implementation.

2. Discover models instead of copying an old model name

Keep the real API key outside source code, screenshots, browser JavaScript, and
shared prompts. In a server-side shell, assign it to an environment variable:

export XPLA_API_KEY="replace_with_your_key"

curl --request GET \
  --url https://xplaai.com/v1/models \
  --header "Authorization: Bearer $XPLA_API_KEY"

Treat the response as a current capability input, not a permanent catalog.
Before you expose a model in your product, record:

1. its exact public name;
2. the endpoint family it belongs to;
3. the accepted fields;
4. whether the result is synchronous or asynchronous;
5. the last contract-review date;
6. the output checks required by your application.

Do not silently replace one model with another when their parameters differ.

3. Build a model-contract registry

A route adapter should not accept every possible field and forward it blindly.
Instead, keep an explicit registry:

type ModelContract = {
  route: '/v1/images/generations' | '/v1/videos';
  allowedFields: readonly string[];
  result: 'synchronous' | 'asynchronous';
  reviewedAt: string;
};

const contracts: Record<string, ModelContract> = {
  'gpt-image-2': {
    route: '/v1/images/generations',
    allowedFields: ['model', 'prompt', 'size', 'images', 'quality'],
    result: 'synchronous',
    reviewedAt: '2026-08-31',
  },
  'veo-3.1-fast': {
    route: '/v1/videos',
    allowedFields: [
      'model',
      'prompt',
      'seconds',
      'resolution',
      'ratio',
      'images',
      'metadata',
    ],
    result: 'asynchronous',
    reviewedAt: '2026-08-31',
  },
};

This is an illustrative registry based on a dated contract review. Generate
production values from the documentation and tests your team has actually
approved.

The review date should trigger revalidation. It is not decorative metadata.

4. Separate synchronous results from asynchronous tasks

Supported image-generation contracts can return a result in the initial
response. Video creation requires a task lifecycle:

1. send POST /v1/videos;
2. persist the returned task ID;
3. poll GET /v1/videos/{task_id} with bounded intervals;
4. stop polling on a documented terminal state;
5. retrieve ready content through GET /v1/videos/{task_id}/content;
6. send the output to rights and quality review.

Do not keep a task ID only in browser memory. A refresh, worker restart, or
temporary network failure should not make the application lose the job.

5. Normalize errors without erasing the original cause

Your product can present a small internal error taxonomy, but preserve the
original route, public model name, status, and task ID.

Signal	Application action	Avoid
401	stop and request a valid server-side token	sending the key to client analytics
400 or validation error	show the rejected field and selected contract	retrying the same invalid body
429	use bounded backoff and show availability state	unlimited concurrent retries
terminal task failure	preserve task ID and reason	reporting success because task creation returned an ID
authenticated or temporary content URL	retrieve through the documented flow	treating it as a permanent public asset
unsupported region or account	disable the action and explain the requirement	implying universal availability

A gateway does not remove upstream or model failure modes. It gives the
application one public access boundary from which to handle them.

6. Add observability before adding more models

For each request, consider recording:

• an internal request ID with no customer secret;
• route and public model name;
• timestamp and application version;
• an input hash instead of private raw media where possible;
• task ID for asynchronous work;
• current state and terminal reason;
• output location and retention policy;
• retry count;
• review decision.

Do not log a full authorization header, API key, private signed URL, or
unrestricted customer prompt by default.

7. Treat API success and production approval as separate gates

A 200 response or a completed task proves that the technical request
finished. It does not prove that:

• product identity is accurate;
• text and claims are correct;
• the media is licensed for its intended use;
• the result fits the destination platform;
• retention and privacy requirements were met.

Merchant image and video workflows need a second approval gate for product
truth, rights, output quality, and storage.

When should you use an API instead of a packaged workflow?

Use the raw API when your team wants to own:

• the user interface and database;
• the contract registry;
• task queues and retry behavior;
• storage and retention;
• approvals and cost controls;
• output QA and support.

Use a packaged Commerce Skill when you want a repeatable workflow that
coordinates multiple steps and reports its evidence and approval gates. A
Skill does not eliminate model cost, rights review, or human judgment; it
changes how the workflow is organized.

Limitations to plan for

• One key does not mean one schema.
• Not every route is OpenAI-compatible.
• Model lists and account availability can change.
• Route registration does not prove every account can use every model.
• Price, credits, latency, throughput, and uptime need current first-party checks.
• Generated or parsed media still needs rights and output review.
• A unified API does not guarantee lower cost or better reliability.

FAQ

What does “unified AI API” mean?

It means that selected task families share an access layer, base URL,
authentication pattern, and route-discovery process. It should not mean that
all models use one body or response schema.

Does every endpoint use one request format?

No. Image, video, speech, chat, and commerce routes have separate contracts.
Validate only the fields documented for the selected model and route.

Is every XPLA route OpenAI-compatible?

No. The chat route follows the Chat Completions contract. Do not apply one
global compatibility assumption to image, video, speech, or commerce routes.

How should an application handle video generation?

Persist the task ID, poll at bounded intervals, stop on a terminal state, and
retrieve content through the documented authenticated route.

Does a unified API guarantee lower cost or higher uptime?

No. Those claims require current pricing and controlled operational evidence.
An access layer alone cannot prove them.

Related resources

• Maintained XPLA unified AI API guide
• AI image generation API
• AI video API
• Commerce Skills

Disclosure: I prepared this tutorial for XPLA after rechecking the maintained guide and route contracts on September 1, 2026. I have not included a paid result, customer case, traffic claim, or ranking promise.