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Capabilities Overview

Capabilities are modular units that extend what an agent can do. Each capability can contribute:

  • Tools — callable functions the agent can invoke during conversations
  • System prompt additions — context and instructions prepended to the agent’s prompt
  • Features — UI elements unlocked when the capability is active (e.g., Workspace tab)

Agents compose capabilities — enable only what you need.

Fundamental capabilities for file operations, command execution, web access, session management, time awareness, task tracking, scheduling, and agent coordination.

CapabilityIDTools
File Systemsession_file_system6
Bashkit Shellbashkit_shell1
Sessionsession2
Storagesession_storage2
Web Fetchweb_fetch1
Current Timecurrent_time1
Message Metadatamessage_metadata0
Task Managementstateless_todo_list1
Schedulessession_schedule3
Sub Agentssubagents3
AGENTS.mdagent_instructions0
Agent Skillsskills2

Cloud and container sandbox environments for isolated code execution.

CapabilityIDTools
Daytonadaytona10
Deno Sandboxesdeno6
E2Be2b6
Docker Containerdocker_container5

Browser automation and web interaction capabilities.

CapabilityIDTools
Browserlessbrowserless7

Structured data and knowledge capabilities.

CapabilityIDTools
SQL Databasesession_sql_database3

Image generation and editing workflows.

CapabilityIDTools
OpenAI Image Generationgpt_image_gen2

Provider-executed and built-in tool capabilities.

CapabilityIDTools
OpenRouter Server Toolsopenrouter_server_tools0

External-service capabilities and blueprint-backed workflows.

CapabilityIDTools
GitHub Scoutgithub_scout0

Agent self-management and platform control.

CapabilityIDTools
Platform Managementplatform_management14

Performance and cost optimization for LLM interactions.

CapabilityIDTools
Infinity Contextinfinity_context1
Auto Tool Searchauto_tool_search1
OpenAI Tool Searchopenai_tool_search0
Claude Tool Searchclaude_tool_search0
Tool Searchtool_search1
Budgetingbudgeting1
Self-Budgetself_budget0
Parallel Tool Callsparallel_tool_calls0

Streaming-output guardrails and runtime safety nets.

CapabilityIDTools
Prompt Canary Guardrailprompt_canary_guardrail0
Tool Call Repairtool_call_repair0
Guardrailsguardrails0

The guardrails capability runs config-driven deterministic checks (regex, blocklist, tool-call patterns) over model output and tool activity, blocking or logging per check. Configure it per agent; use advisory mode and the POST /v1/capabilities/guardrails/dry-run endpoint to tune checks against false positives before enforcing. For ready-made starting points, list the gallery at GET /v1/capabilities/guardrails/examples (secret detection, PII, profanity, dangerous-shell, prompt-injection heuristics) and drop a preset’s config into the agent’s guardrails capability config.

Run shell commands at lifecycle and tool events. Block, mutate, or audit agent actions from outside the model.

CapabilityIDTools
User Hooksuser_hooks0

Pre-built domain simulations for testing and demonstrations.

CapabilityIDTools
Fake Warehousefake_warehouse10
Fake AWSfake_aws11
Fake CRMfake_crm8
Terminal window
curl -X POST http://localhost:9300/api/v1/agents \
-H "Content-Type: application/json" \
-d '{
"name": "My Agent",
"system_prompt": "You are a helpful assistant.",
"capabilities": ["session_file_system", "bashkit_shell", "web_fetch"]
}'
  1. Navigate to the Agent detail page
  2. Open the Capabilities section
  3. Toggle capabilities on/off
  4. Reorder with drag handles (order affects system prompt priority)
  5. Save
Terminal window
curl http://localhost:9300/api/v1/capabilities

Declarative capabilities are persisted capability definitions made from data: system prompt text, scoped MCP servers, text file mounts, and skill packages. They use a public resource ID like cap_... and a stable capability reference like declarative:research_pack.

Terminal window
curl -X POST http://localhost:9300/api/v1/capabilities \
-H "Content-Type: application/json" \
-d '{
"definition": {
"name": "research_pack",
"display_name": "Research Pack",
"description": "Default research behavior and resources.",
"system_prompt": "Prefer primary sources and cite them clearly.",
"risk_level": "low"
}
}'

Agents and harnesses can use the canonical reference:

{ "ref": "declarative:research_pack" }

For convenience, agent and harness write APIs also accept the plain unique name when it matches a declarative capability:

{ "ref": "research_pack" }

Some capabilities depend on others. Dependencies are resolved automatically at runtime — you don’t need to manually add them.

CapabilityDepends On
Bashkit ShellFile System
Agent SkillsFile System
GitHub ScoutSub Agents
Deno SandboxesStorage
E2BStorage

Capabilities declare UI features they contribute. The session aggregates features from all active capabilities to decide which UI tabs to render.

FeatureUI ElementContributed By
file_systemWorkspace tabFile System, Bashkit Shell
secretsStorage tabStorage
key_valueStorage tabStorage
schedulesSchedules tabSchedules
sql_databaseDatabase tabSQL Database
subagentsSubagents tabSub Agents

Capabilities are applied in the order configured on the agent. Earlier capabilities’ system prompt additions appear first. Place the most important context-setting capabilities first.

  • Concepts — how capabilities fit into the Harness → Agent → Session model
  • API Reference — full API documentation
  • MCP Servers — external tool servers as virtual capabilities