Configuration Overview

docker-agent uses YAML or HCL configuration files to define agents, models, tools, and their relationships.

File Structure

A docker-agent config can be written in YAML or HCL. The examples on this page use YAML; see HCL Configuration for the block-based HCL syntax.

A docker-agent config has these main sections:

# 1. Version — configuration schema version (optional but recommended)
version: 10

# 2. Metadata — optional agent metadata for distribution
metadata:
  author: my-org
  description: My helpful agent
  version: "1.0.0"

# 3. Models — define AI models with their parameters
models:
  claude:
    provider: anthropic
    model: claude-sonnet-4-5
    max_tokens: 64000

# 4. Agents — define AI agents with their behavior
agents:
  root:
    model: claude
    description: A helpful assistant
    instruction: You are helpful.
    toolsets:
      - type: think

# 5. RAG — define retrieval-augmented generation sources (optional)
rag:
  docs:
    docs: ["./docs"]
    strategies:
      - type: chunked-embeddings
        embedding_model: openai/text-embedding-3-small

# 6. MCPs — reusable MCP server definitions (optional)
mcps:
  github:
    remote:
      url: https://api.githubcopilot.com/mcp
      transport_type: sse

# 7. Providers — optional reusable provider definitions
providers:
  my_provider:
    provider: anthropic  # or openai (default), google, amazon-bedrock, etc.
    token_key: MY_API_KEY
    max_tokens: 16384

# 8. Permissions — agent-level tool permission rules (optional)
#    For user-wide global permissions, see ~/.config/cagent/config.yaml
permissions:
  allow: ["read_*"]
  deny: ["shell:cmd=sudo*"]

# 9. Commands & Skills — reusable, named groups shared across agents (optional)
commands:
  ci:
    deploy: "Deploy the application"
skills:
  base: [local, git]

# 10. Toolsets — reusable, named toolset definitions shared across agents (optional)
toolsets:
  fs:
    type: filesystem

Minimal Config

The simplest possible configuration — a single agent with an inline model:

agents:
  root:
    model: openai/gpt-5
    description: A helpful assistant
    instruction: You are a helpful assistant.

The same config in HCL:

agent "root" {
  model       = "openai/gpt-5"
  description = "A helpful assistant"
  instruction = "You are a helpful assistant."
}

Inline vs Named Models

Models can be referenced inline or defined in the models section:

• Inline — quick and simple. Use provider/model syntax directly: model: openai/gpt-5
• Named — full control over parameters, reusable across agents: model: my_claude

Config Sections

• HCL Configuration — write the same agent schema in HCL using labeled blocks, heredocs, and block-based tool definitions.
• Agent Config — all agent properties: model, instruction, tools, sub-agents, hooks, and more.
• Model Config — provider setup, parameters, thinking budget, and provider-specific options.
• Tool Config — built-in tools, MCP tools, Docker MCP, LSP, API tools, and tool filtering.

Advanced Configuration

• Hooks — run shell commands at lifecycle events like tool calls and session start/end.
• Permissions — control which tools auto-approve, require confirmation, or are blocked.
• Sandbox Mode — run agents in an isolated Docker container for security.
• Structured Output — constrain agent responses to match a specific JSON schema.

Environment Variables

API keys and secrets are read from environment variables — never stored in config files. See Managing Secrets for all the ways to provide credentials (env files, Docker Compose secrets, macOS Keychain, pass):

Tool Auto-Installation:

Runtime overrides:

Note

Legacy CAGENT_* aliases

The same variables are also accepted with the legacy CAGENT_ prefix (e.g. CAGENT_DEFAULT_MODEL, CAGENT_MODELS_GATEWAY, CAGENT_HIDE_TELEMETRY_BANNER) for backward compatibility. Prefer the DOCKER_AGENT_* form in new setups.

Important

Model references are case-sensitive: openai/gpt-5 is not the same as openai/GPT-5.

Variable Expansion in Config Fields

docker-agent expands ${env.VAR} references in many config fields. This is the canonical syntax everywhere — prefer it for every field. Two engines back it: a full JavaScript evaluator for prompt/HTTP fields (where you also get defaults, ternaries, and tool calls), and a simpler path expander for filesystem/env fields (which additionally accepts the legacy $VAR / ${VAR} / ~ shell forms). Picking ${env.VAR} everywhere always works; the one caveat is that the path expander does not evaluate richer JS expressions. Using a shell-style $VAR in a JS-templated field is currently a silent no-op, so the literal string is passed through. Tracking issue: #2615.

JavaScript template literals — ${env.VAR}

Used wherever the agent prompt or HTTP traffic is templated. Backed by a JS evaluator, so you also get || defaults, ternaries, and tool calls (${tool({...})}).

Applies to:

• agents.<name>.description
• agents.<name>.welcome_message
• agents.<name>.instruction
• agents.<name>.commands.* (string form and instruction: field)
• toolsets[*].instruction
• toolsets[*].headers and toolsets[*].remote.headers (MCP, A2A, OpenAPI, fetch, API)

For api toolsets, api_config.endpoint and api_config.headers are also rendered through the JS expander (the same syntax applies).

agents:
  root:
    description: "Assistant for ${env.USER || 'guest'}"
    commands:
      deploy: "Deploy ${env.PROJECT_NAME || 'app'} to ${env.ENV || 'staging'}"
    toolsets:
      - type: openapi
        url: https://api.example.com
        headers:
          Authorization: "Bearer ${env.INTERNAL_TOKEN}"

Undefined variables expand to the empty string.

Path & env fields — ${env.VAR} (canonical), $VAR / ${VAR} / ~ (aliases)

Used for filesystem paths and process environment values. Backed by os.ExpandEnv plus tilde expansion against the current user's home directory. The canonical ${env.VAR} form is accepted here too, so a single syntax works across every field; the bare $VAR / ${VAR} shell forms remain supported as aliases.

Applies to:

• agents.<name>.toolsets[*].working_dir (MCP, LSP)
• agents.<name>.toolsets[*].path (memory, tasks)
• agents.<name>.toolsets[*].env values (MCP, shell, script, LSP)
• The ~ prefix is also accepted in any path-like field documented as such.

agents:
  root:
    toolsets:
      - type: memory
        path: "~/notes/${env.PROJECT}/memory.db"
      - type: mcp
        command: my-server
        working_dir: "${env.HOME}/work"

Unlike the JS-templated fields above, these accept only a plain variable reference: richer JS expressions (e.g. ${env.VAR || 'default'}) are not evaluated here, and the legacy $VAR / ${VAR} forms keep working for backward compatibility.

Model definitions follow the same rule. The models.<name>.model and models.<name>.base_url fields are expanded when the provider is built, accepting both ${env.VAR} and ${VAR}. This is useful when the model id or endpoint is injected by the environment (for example a Docker Compose / DMR setup that exports the model reference as a variable):

models:
  nemotron3:
    provider: dmr
    model: "${env.NEMOTRON3_MODEL}" # resolved from the environment at load time
    base_url: "${DMR_BASE_URL}"     # ${VAR} is accepted as well

token_key is not expanded: it already names the environment variable that holds the API token, so its value is used as a key rather than substituted. An unset variable in model or base_url is reported as an error instead of dialing with an empty value.

Quick reference

The ~ prefix is meaningful only in path-like fields (working_dir, path).

Prefer ${env.X} everywhere. The bare $X / ${X} and ~ forms are accepted only in path and env value fields, where they remain supported for backward compatibility.

Validation

docker-agent validates your configuration at startup:

• Local sub_agents must reference agents defined in the config (external OCI references like agentcatalog/pirate are pulled from registries automatically; pin them to a digest with @sha256:… to avoid a per-run registry lookup)
• Named model references must exist in the models section
• Provider names must be valid (openai, anthropic, google, dmr, etc.)
• Required environment variables (API keys) must be set
• Tool-specific fields are validated (e.g., path is only valid for memory)

JSON Schema

For YAML editor autocompletion and validation, use the Docker Agent JSON Schema. Add this to the top of your YAML file:

# yaml-language-server: $schema=https://raw.githubusercontent.com/docker/docker-agent/main/agent-schema.json

Config Versioning

docker-agent configs are versioned. The current version is 10. Add the version at the top of your config:

version: 10

agents:
  root:
    model: openai/gpt-5
    # ...

When you load an older config, docker-agent automatically migrates it to the latest schema. It's recommended to include the version to ensure consistent behavior.

Metadata Section

Optional metadata for agent distribution via OCI registries:

metadata:
  author: my-org
  license: Apache-2.0
  description: A helpful coding assistant
  readme: | # Displayed in registries
    This agent helps with coding tasks.
  version: "1.0.0"
  tags: [coding, review]

See Agent Distribution for publishing agents to registries.

Reusable MCP Servers (mcps:)

The top-level mcps: section defines named MCP server configurations that agents can reference with toolsets: [{type: mcp, ref: <name>}]. This avoids repeating the same command / URL / headers across agents and keeps credentials in one place.

mcps:
  github:
    remote:
      url: https://api.githubcopilot.com/mcp
      transport_type: sse
  playwright:
    command: npx
    args: ["-y", "@modelcontextprotocol/server-playwright"]

agents:
  root:
    model: openai/gpt-5
    toolsets:
      - type: mcp
        ref: github        # reuse the definition above
      - type: mcp
        ref: playwright

An mcps entry accepts every field a regular type: mcp toolset accepts (command/args/env, remote with url/transport_type/headers/oauth, tools filter, instruction, defer, …) — the type: mcp is implicit. See the Tool Config page for all options and the Remote MCP Servers guide for remote setups.

Reusable Toolsets (toolsets:)

The top-level toolsets: map defines named toolset configurations that agents can reference by name through use_toolsets:. This avoids repeating the same toolset definition across multiple agents — the same pattern as mcps: for MCP servers and commands: / skills: for reusable prompt groups.

Any toolset type is supported, including ones that reference MCP or RAG definitions. Shared toolsets are resolved before the MCP/RAG pass, so they can contain {type: mcp, ref: <name>} references.

toolsets:
  fs:               # a named shared toolset
    type: filesystem
  docs:
    type: fetch
    allowed_domains:
      - docker.com

agents:
  root:
    model: openai/gpt-5
    # Pull in shared toolsets by name; inline toolsets come first.
    use_toolsets: [fs, docs]
    toolsets:
      - type: think

  reviewer:
    model: openai/gpt-5
    # Reuse the same filesystem toolset without copying its definition.
    use_toolsets: [fs]

Inline toolsets: entries listed directly on the agent take precedence in ordering (they come first) and are always included alongside referenced ones.

See examples/shared-toolsets.yaml for a complete example.

Reusable Commands & Skills (commands: / skills:)

The top-level commands: and skills: sections define named, reusable groups that agents pull in by name through use_commands: / use_skills:. This avoids repeating the same command set or skill configuration across agents. Each group value uses the exact same format as an agent's own commands / skills field.

Referenced groups are merged into the agent during config loading. An agent's own inline commands / skills entries take precedence on name conflicts.

commands:
  ci:                       # a named command group
    deploy: "Deploy the application"
    test: "Run the test suite"
skills:
  base: [local, git]        # a named skill group

agents:
  root:
    model: openai/gpt-5
    use_commands: [ci]        # reuse the "ci" command group
    use_skills: [base]        # reuse the "base" skill group
    commands:
      lint: "Run the linter"  # inline command, merged in (wins on conflict)
  reviewer:
    model: openai/gpt-5
    use_commands: [ci]        # same group, reused without duplication

See examples/shared-commands-skills.yaml for a complete example.

Custom Providers Section

Define reusable provider configurations with shared defaults. Providers can wrap any provider type — not just OpenAI-compatible endpoints:

providers:
  # OpenAI-compatible custom endpoint
  azure:
    api_type: openai_chatcompletions
    base_url: https://my-resource.openai.azure.com/openai/deployments/gpt-4o
    token_key: AZURE_OPENAI_API_KEY

  # Anthropic with shared model defaults
  team_anthropic:
    provider: anthropic
    token_key: TEAM_ANTHROPIC_KEY
    max_tokens: 32768
    thinking_budget: 16384

models:
  azure_gpt:
    provider: azure
    model: gpt-4o

  claude:
    provider: team_anthropic
    model: claude-sonnet-4-5
    # Inherits max_tokens, thinking_budget from provider

agents:
  root:
    model: claude

See Provider Definitions for more details.

Reusable YAML (anchors & aliases)

YAML anchors (&name), aliases (*name) and merge keys (<<) are part of the YAML spec, and Docker Agent's config parser supports them. Use them to declare a value once and reuse it elsewhere in the same file, instead of copy-pasting the same block across agents.

This complements the named-reuse sections above (mcps:, commands: / skills:, providers:). Reach for anchors when you want to share something those sections don't cover, such as an instruction string or a block of agent settings.

Reuse a value verbatim with an anchor and an alias:

agents:
  root:
    model: anthropic/claude-sonnet-4-5
    description: Coordinator.
    instruction: &house_rules |
      You are part of the Acme engineering team.
      Cite the files you looked at and keep changes minimal.
  reviewer:
    model: anthropic/claude-sonnet-4-5
    description: Reviews code changes.
    instruction: *house_rules        # the same instruction, declared once

Compose a block with a merge key (<<), then override individual fields:

agents:
  reviewer: &specialist
    model: anthropic/claude-sonnet-4-5
    description: Reviews code changes.
    instruction: |
      You are a meticulous software professional.
    toolsets:
      - type: filesystem
  documenter:
    <<: *specialist                   # inherit model, instruction, toolsets
    description: Writes documentation. # then override one field

Warning

Where anchors can live

An anchor has to sit on a real value inside a known section (for example a real agent, model, or MCP entry, as above). Parking anchors in a separate top-level block such as defaults: or prompts: fails, because the parser rejects unknown top-level keys.

Warning

Overriding merged keys

Overriding a key that a << merge already set works only in the agents: section, as shown above. Every other section (models:, mcps:, providers:, rag:) is parsed strictly and reports the override as a duplicate key. There, use << only to add new fields, or use the named-reuse sections above when you need per-entry overrides.

Anchors are for static reuse within a single file, not dynamic values or cross-file composition. For environment-specific settings, see Variable Expansion in Config Fields, which substitutes ${env.VAR} at load time. Templating tags such as !include are not acted on: the tag is ignored and its argument is kept as a plain string, so no other file is loaded. Circular aliases are not detected, so keep references acyclic.

See examples/yaml-anchors.yaml for a complete example.