Haiku 5.5 API quickstart

A Haiku 5.5 API integration needs a provider account, a server-side credential and a request that matches that provider's protocol. Begin with one small text request. Confirm authentication, model selection and response parsing before adding streaming, tools or a large document. This keeps the first failure narrow enough to diagnose.

The example here targets Anthropic's native Messages API. It is illustrative and has not been executed using a paid account for this article. This website uses a gateway connection for its own workspace; buying site credits does not issue an Anthropic API key or create an API account for you.

Choose the Haiku 5.5 API provider first

The model name alone does not identify the complete integration. Anthropic's API, a cloud deployment and a gateway can use different authentication, request formats and model identifiers. Start with the account that will receive the bill. Its documentation is the authority for the endpoint and supported features.

Anthropic documents the native model identifier as claude-haiku-5-5. Gateways may use a provider-prefixed name. Do not copy an identifier from one service into another and assume the server will translate it. A model-not-found response can be a naming or account-access problem rather than proof that the model does not exist.

Keep endpoint selection in trusted server configuration. A user-controlled endpoint field paired with your server's API key can send credentials to an unintended host. If your product supports several providers, use an explicit allowlist and a separate credential for each route. The ZenMux guide addresses that gateway separately.

Protect your Haiku 5.5 API credential

Read the key from an environment variable in your server process. Do not place it in a public JavaScript bundle, a shareable URL, a browser screenshot or a committed example file. Local development files should be excluded from version control, and deployed environments should use the hosting platform's secret configuration.

Your users should authenticate to your application, not receive your provider credential. The application checks their permissions and usage policy before constructing the upstream request. A hidden button is not an access-control boundary: the server still needs to validate the submitted model, input size and account state.

Use a disposable test credential with an appropriate spending limit when testing a new Haiku 5.5 API integration. Rotate a key if it is exposed. Deleting it from a file after publication does not remove it from repository history, logs or a recipient's copy. Do not print an environment dump as part of a debugging routine.

Send a minimal Haiku 5.5 API request

The following Bash example uses an already configured ANTHROPIC_API_KEY. It sends a deliberately small synthetic task to the documented Messages endpoint. Executing it can incur provider charges. The command does not configure this website or use a site credit balance.

curl --fail-with-body https://api.anthropic.com/v1/messages \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "content-type: application/json" \
  --data '{
    "model": "claude-haiku-5-5",
    "max_tokens": 2048,
    "messages": [
      {"role": "user", "content": "Classify this synthetic request as billing or technical: Please resend my invoice. Return the label only."}
    ]
  }'

The expected task answer is the billing label, but the transport response is a structured message rather than a bare label. The chosen output budget is a starting point for this example, not a promise that every request will complete within it. Inspect the returned completion state before treating any visible text as final.

Avoid importing old sampling settings into this first request. The model-specific migration guide identifies compatibility changes that generic Messages examples may not reflect. Model-specific restrictions take precedence over an older example that happens to use the same endpoint.

Parse the Haiku 5.5 API response

Select text blocks by type instead of assuming the first content block is the answer. A response may contain other block types, and an empty text result deserves an explicit application state. Store enough sanitized metadata to distinguish an empty answer from a parsing bug or a response that stopped before producing text.

Check the stop reason. A response that reaches its output limit is not automatically a complete answer, and a refusal is not a retryable transport failure. For structured tasks, validate the extracted text against your application schema after parsing the provider envelope. Correct JSON syntax alone does not prove the values match the source.

Keep the original provider response available only under an appropriate retention and access policy. Operational logs usually need request IDs, duration, model and usage counters, not the full confidential prompt. This division makes a Haiku 5.5 API incident easier to investigate without turning every log viewer into a reader of customer content.

Handle Haiku 5.5 API failures deliberately

A malformed request needs a code or input change. Retrying the same invalid body wastes time and can make the error harder to see. An authentication failure needs credential or account investigation. A temporary rate limit may justify waiting, but only within a bounded retry policy that respects the provider's response headers.

Set a total request deadline and an attempt limit. If a client library retries automatically and your application also retries, the combined number of upstream calls can exceed what either layer appears to allow. Decide which layer owns retries and document that decision. Never assume a network timeout proves the provider did no work.

Use an application job identifier to prevent duplicate downstream effects. Generating the same draft twice is inconvenient; sending it twice or applying a business action twice is more serious. Keep generation, validation and any external action as separate stages so a retry cannot silently repeat all three.

Track usage without inventing precision

Record the usage fields returned by your actual provider. A Haiku 5.5 API estimate based on character length is not equivalent to a tokenizer count, and a count from another model is not a reliable substitute. Where available, use the provider's counting endpoint before planning a large request.

Distinguish input, output and cache-related categories according to the provider's schema. Reasoning may be included in billable output rather than appearing as visible prose. Do not add a reasoning field to output a second time unless the billing documentation explicitly defines the fields as disjoint. Store the pricing version separately from the measured usage.

For public manufacturer estimates, use the official price page. For this website, credit usage follows its published credit rules and the actual connected route. Presenting those two accounting systems as identical would give users an inaccurate expectation of what a purchased credit pack buys.

Add features one at a time

Once the minimal request works, add your system message and a representative input. Then test any structured-output requirement. Streaming and tool execution deserve their own lifecycle tests because they introduce partial results, cancellation and additional messages. A successful non-streaming call does not verify those paths.

Keep small offline response fixtures for your parser and error handling. These can prove that your application handles multiple blocks, missing fields and truncated results without paid requests. Separately label the live smoke test that verifies account access. Combining both under a single green check makes it unclear which behavior has actually been exercised.

Before production use, review authentication, spending controls, input validation and logging. A working Haiku 5.5 API call is only one part of a working feature. The surrounding application must still protect the credential, enforce user permissions and explain failures in terms a person can act on.

A practical completion checklist

You are ready for a limited rollout when the exact provider route is documented, the credential remains server-side and a known synthetic task produces a validated result. You should also be able to demonstrate how the application handles an invalid request, a temporary limit and an incomplete answer without double-submitting a job.

Keep a record of what remains untested. File inputs, tools and long context do not become verified because a short text request succeeded. Start with the text workspace when you only need to evaluate prompts; use your own API project when you need to verify transport behavior. That distinction keeps the Haiku 5.5 API quickstart small enough to understand and honest about what it proves.