LLM Providers

For each model provider, you can configure parameters either through environment variables or in your fastagent.config.yaml file.

Be sure to run fast-agent check to troubleshoot API Key issues:

Key Check

Common Configuration Format

In your fastagent.config.yaml:

<provider>:
  api_key: "your_api_key" # Override with API_KEY env var
  base_url: "https://api.example.com" # Base URL for API calls

Anthropic

Anthropic models support Text, Vision and PDF content.

YAML Configuration:

anthropic:
  api_key: "your_anthropic_key" # Required
  base_url: "https://api.anthropic.com/v1" # Default, only include if required

Environment Variables:

ANTHROPIC_API_KEY: Your Anthropic API key
ANTHROPIC_BASE_URL: Override the API endpoint

Model Name Aliases:

Model Alias	Maps to
`claude`	`claude-3-7-sonnet-latest`
`sonnet`	`claude-3-7-sonnet-latest`
`sonnet35`	`claude-3-5-sonnet-latest`
`sonnet37`	`claude-3-7-sonnet-latest`
`haiku`	`claude-3-5-haiku-latest`
`haiku3`	`claude-3-haiku-20240307`
`haiku35`	`claude-3-5-haiku-latest`
`opus`	`claude-3-opus-latest`
`opus3`	`claude-3-opus-latest`

OpenAI

fast-agent supports OpenAI gpt-4.1, gpt-4.1-mini, o1-preview, o1 and o3-mini models. Arbitrary model names are supported with openai.<model_name>. Supported modalities are model-dependent, check the OpenAI Models Page for the latest information.

Structured outputs use the OpenAI API Structured Outputs feature.

Future versions of fast-agent will have enhanced model capability handling.

YAML Configuration:

openai:
  api_key: "your_openai_key" # Default
  base_url: "https://api.openai.com/v1" # Default, only include if required

Environment Variables:

OPENAI_API_KEY: Your OpenAI API key
OPENAI_BASE_URL: Override the API endpoint

Model Name Aliases:

Model Alias	Maps to
`gpt-4o`	`gpt-4o`
`gpt-4o-mini`	`gpt-4o-mini`
`gpt-4.1`	`gpt-4.1`
`gpt-4.1-mini`	`gpt-4.1-mini`
`gpt-4.1-nano`	`gpt-4.1-nano`
`o1`	`o1`
`o1-mini`	`o1-mini`
`o1-preview`	`o1-preview`
`o3-mini`	`o3-mini`

DeepSeek

DeepSeek v3 is supported for Text and Tool calling.

YAML Configuration:

deepseek:
  api_key: "your_deepseek_key"
  base_url: "https://api.deepseek.com/v1"

Environment Variables:

DEEPSEEK_API_KEY: Your DeepSeek API key
DEEPSEEK_BASE_URL: Override the API endpoint

Model Name Aliases:

Model Alias	Maps to
`deepseek`	`deepseek-chat`
`deepseek3`	`deepseek-chat`

Google

Google is currently supported through the OpenAI compatibility endpoint, with first-party support planned soon.

YAML Configuration:

google:
  api_key: "your_google_key"
  base_url: "https://generativelanguage.googleapis.com/v1beta/openai"

Environment Variables:

GOOGLE_API_KEY: Your Google API key

Model Name Aliases:

None mapped

Generic OpenAI / Ollama

Models prefixed with generic will use a generic OpenAI endpoint, with the defaults configured to work with Ollama OpenAI compatibility.

This means that to run Llama 3.2 latest you can specify generic.llama3.2:latest for the model string, and no further configuration should be required.

Warning

The generic provider is tested for tool calling and structured generation with qwen2.5:latest and llama3.2:latest. Other models and configurations may not work as expected - use at your own risk.

YAML Configuration:

generic:
  api_key: "ollama" # Default for Ollama, change as needed
  base_url: "http://localhost:11434/v1" # Default for Ollama

Environment Variables:

GENERIC_API_KEY: Your API key (defaults to ollama for Ollama)
GENERIC_BASE_URL: Override the API endpoint

Usage with other OpenAI API compatible providers: By configuring the base_url and appropriate api_key, you can connect to any OpenAI API-compatible provider.

OpenRouter

Uses the OpenRouter aggregation service. Models are accessed via an OpenAI-compatible API. Supported modalities depend on the specific model chosen on OpenRouter.

Models must be specified using the openrouter. prefix followed by the full model path from OpenRouter (e.g., openrouter.google/gemini-flash-1.5).

YAML Configuration:

openrouter:
  api_key: "your_openrouter_key" # Required
  base_url: "https://openrouter.ai/api/v1" # Default, only include to override

Environment Variables:

OPENROUTER_API_KEY: Your OpenRouter API key
OPENROUTER_BASE_URL: Override the API endpoint

Model Name Aliases:

OpenRouter does not use aliases in the same way as Anthropic or OpenAI. You must always use the openrouter.provider/model-name format.