Anthropic compatibility

Connect Anthropic clients and tools such as Claude Code to Ollama. Ollama supports a subset of the Anthropic Messages API.

Direct cloud access

Set your API key in OLLAMA_API_KEY. No Ollama installation required.

export OLLAMA_API_KEY="your_api_key"

Send a request with bearer authentication:

curl https://ollama.com/v1/messages \
  -H "Authorization: Bearer $OLLAMA_API_KEY" \
  -H "Content-Type: application/json" \
  -H "anthropic-version: 2023-06-01" \
  -d '{
    "model": "gemma4:31b",
    "max_tokens": 1024,
    "messages": [
      {
        "role": "user",
        "content": "Say hello in one sentence."
      }
    ]
  }'

Read text blocks from content. The cloud endpoint requires Authorization: Bearer; it does not accept x-api-key alone. Compatible models support messages, streaming, and function calling. Tool-choice controls, deferred tools, and hosted web search are not fully supported.

Local server usage

These examples connect to your local Ollama server. Use ollama as the placeholder API key. To use cloud models through this server, sign in to Ollama.

Environment variables

To use Ollama with tools that expect the Anthropic API (like Claude Code), set these environment variables:

export ANTHROPIC_AUTH_TOKEN=ollama  # required but ignored
export ANTHROPIC_BASE_URL=http://localhost:11434

Simple `/v1/messages` example

basic.py

import anthropic

client = anthropic.Anthropic(
    base_url='http://localhost:11434',
    api_key='ollama',  # required but ignored
)

message = client.messages.create(
    model='qwen3-coder',
    max_tokens=1024,
    messages=[
        {'role': 'user', 'content': 'Hello, how are you?'}
    ]
)
print(message.content[0].text)

import Anthropic from "@anthropic-ai/sdk";

const anthropic = new Anthropic({
  baseURL: "http://localhost:11434",
  apiKey: "ollama", // required but ignored
});

const message = await anthropic.messages.create({
  model: "qwen3-coder",
  max_tokens: 1024,
  messages: [{ role: "user", content: "Hello, how are you?" }],
});

console.log(message.content[0].text);

curl -X POST http://localhost:11434/v1/messages \
-H "Content-Type: application/json" \
-H "x-api-key: ollama" \
-H "anthropic-version: 2023-06-01" \
-d '{
  "model": "qwen3-coder",
  "max_tokens": 1024,
  "messages": [{ "role": "user", "content": "Hello, how are you?" }]
}'

Streaming example

streaming.py

import anthropic

client = anthropic.Anthropic(
    base_url='http://localhost:11434',
    api_key='ollama',
)

with client.messages.stream(
    model='qwen3-coder',
    max_tokens=1024,
    messages=[{'role': 'user', 'content': 'Count from 1 to 10'}]
) as stream:
    for text in stream.text_stream:
        print(text, end='', flush=True)

import Anthropic from "@anthropic-ai/sdk";

const anthropic = new Anthropic({
  baseURL: "http://localhost:11434",
  apiKey: "ollama",
});

const stream = await anthropic.messages.stream({
  model: "qwen3-coder",
  max_tokens: 1024,
  messages: [{ role: "user", content: "Count from 1 to 10" }],
});

for await (const event of stream) {
  if (
    event.type === "content_block_delta" &&
    event.delta.type === "text_delta"
  ) {
    process.stdout.write(event.delta.text);
  }
}

curl -X POST http://localhost:11434/v1/messages \
-H "Content-Type: application/json" \
-d '{
  "model": "qwen3-coder",
  "max_tokens": 1024,
  "stream": true,
  "messages": [{ "role": "user", "content": "Count from 1 to 10" }]
}'

Tool calling example

tools.py

import anthropic

client = anthropic.Anthropic(
    base_url='http://localhost:11434',
    api_key='ollama',
)

message = client.messages.create(
    model='qwen3-coder',
    max_tokens=1024,
    tools=[
        {
            'name': 'get_weather',
            'description': 'Get the current weather in a location',
            'input_schema': {
                'type': 'object',
                'properties': {
                    'location': {
                        'type': 'string',
                        'description': 'The city and state, e.g. San Francisco, CA'
                    }
                },
                'required': ['location']
            }
        }
    ],
    messages=[{'role': 'user', 'content': "What's the weather in San Francisco?"}]
)

for block in message.content:
    if block.type == 'tool_use':
        print(f'Tool: {block.name}')
        print(f'Input: {block.input}')

import Anthropic from "@anthropic-ai/sdk";

const anthropic = new Anthropic({
  baseURL: "http://localhost:11434",
  apiKey: "ollama",
});

const message = await anthropic.messages.create({
  model: "qwen3-coder",
  max_tokens: 1024,
  tools: [
    {
      name: "get_weather",
      description: "Get the current weather in a location",
      input_schema: {
        type: "object",
        properties: {
          location: {
            type: "string",
            description: "The city and state, e.g. San Francisco, CA",
          },
        },
        required: ["location"],
      },
    },
  ],
  messages: [{ role: "user", content: "What's the weather in San Francisco?" }],
});

for (const block of message.content) {
  if (block.type === "tool_use") {
    console.log("Tool:", block.name);
    console.log("Input:", block.input);
  }
}

curl -X POST http://localhost:11434/v1/messages \
-H "Content-Type: application/json" \
-d '{
  "model": "qwen3-coder",
  "max_tokens": 1024,
  "tools": [
    {
      "name": "get_weather",
      "description": "Get the current weather in a location",
      "input_schema": {
        "type": "object",
        "properties": {
          "location": {
            "type": "string",
            "description": "The city and state"
          }
        },
        "required": ["location"]
      }
    }
  ],
  "messages": [{ "role": "user", "content": "What is the weather in San Francisco?" }]
}'

Using with Claude Code

See the Claude Code guide for Ollama Launch and direct cloud setup.

Endpoints

`/v1/messages`

Supported features

Supported request fields

Supported response fields

Streaming events

Use /api/show to discover a model’s supported thinking values and default. thinking.type: "enabled" and "disabled" act as explicit on/off controls. When a model uses its metadata to resolve named levels, supported output_config.effort names are applied exactly and unsupported names resolve to the model default. Models without metadata keep the existing compatibility behavior, which trims and lowercases effort names and maps "xhigh" to "high".

Models

Ollama supports both local and cloud models.

Local models

Pull a local model before use:

ollama pull qwen3-coder

Recommended local models:

qwen3-coder - Excellent for coding tasks
gpt-oss:20b - Strong general-purpose model

Cloud models

Browse the cloud model catalog. Through a signed-in Ollama server, use a cloud name such as gemma4:cloud without a separate pull. For direct cloud requests, use the hosted identifier, such as gemma4:31b.

Default model names on a local server

For tooling that relies on default Anthropic model names such as claude-3-5-sonnet, use ollama cp to copy an existing model name:

ollama cp qwen3-coder claude-3-5-sonnet

Afterwards, this new model name can be specified in the model field:

curl http://localhost:11434/v1/messages \
    -H "Content-Type: application/json" \
    -d '{
        "model": "claude-3-5-sonnet",
        "max_tokens": 1024,
        "messages": [
            {
                "role": "user",
                "content": "Hello!"
            }
        ]
    }'

Differences from the Anthropic API

Behavior differences

The local server does not validate API keys. Direct cloud inference requires a valid bearer token.
The hosted endpoint rejects anthropic-version values older than 2023-06-01. Use 2023-06-01 in requests.
Token counts are approximations based on the underlying model’s tokenizer

Not supported

The following Anthropic API features are not currently supported:

Feature	Description
`/v1/messages/count_tokens`	Token counting endpoint
`tool_choice`	Forcing specific tool use or disabling tools
`metadata`	Request metadata (user_id)
Prompt caching	`cache_control` blocks for caching prefixes
Batches API	`/v1/messages/batches` for async batch processing
Citations	`citations` content blocks
PDF support	`document` content blocks with PDF files
Server-sent errors	`error` events during streaming (errors return HTTP status)

Partial support

Feature	Status
Image content	Base64 images supported; URL images not supported
Extended thinking	Basic support; `budget_tokens` accepted but not enforced

​Direct cloud access

​Local server usage

​Environment variables

​Simple /v1/messages example

​Streaming example

​Tool calling example

​Using with Claude Code

​Endpoints

​/v1/messages

​Supported features

​Supported request fields

​Supported response fields

​Streaming events

​Models

​Local models

​Cloud models

​Default model names on a local server

​Differences from the Anthropic API

​Behavior differences

​Not supported

​Partial support