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homeassistant-ai

Home Assistant MCP Server

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Call Service

ha_call_service
Destructive

Execute Home Assistant services to control entities and trigger automations. Specify domain, service, and entity ID for targeted actions.

Instructions

Execute Home Assistant services to control entities and trigger automations.

This is the universal tool for controlling all Home Assistant entities. Services follow the pattern domain.service (e.g., light.turn_on, climate.set_temperature).

Basic Usage:

# Turn on a light
ha_call_service("light", "turn_on", entity_id="light.living_room")

# Set temperature with parameters
ha_call_service("climate", "set_temperature",
              entity_id="climate.thermostat", data={"temperature": 22})

# Trigger automation
ha_call_service("automation", "trigger", entity_id="automation.morning_routine")

# Universal controls work with any entity
ha_call_service("homeassistant", "toggle", entity_id="switch.porch_light")

Key behavior:

  • wait (default True): wait for the entity state to change before returning. Only applies to state-changing services on a single entity.

  • Result compaction (default ON): result is trimmed to the targeted entity's record (drops parent-group propagation) and stripped of context / last_* metadata and heavy attribute lists (effect_list, hue_scenes). Escape hatches: verbose=True for the raw HA response, or result_fields / result_attribute_keys for explicit per-record projection (mirrors ha_get_state).

For detailed service documentation, use ha_get_skill_guide.

Common patterns: Use ha_get_state() to check current values before making changes. Use ha_search() to find correct entity IDs.

WebSocket command escape hatch (advanced): A few Home Assistant operations are WebSocket-only commands, not registered services — most notably dismissing a Repairs issue. Pass ws_command (instead of domain/service) to send one, with its parameters in data:

# Dismiss a repair (get domain/issue_id from ha_get_overview repairs
# or ha_get_system_health include="repairs")
ha_call_service(ws_command="repairs/ignore_issue",
                data={"domain": "sun", "issue_id": "abc", "ignore": True})

Only one-shot request/response commands are supported; streaming/two-phase and service-invoking commands are rejected, and the other service parameters (entity_id, return_response, etc.) don't apply.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
dataNo
waitNo
domainNo
serviceNo
verboseNoReturn HA's raw service response unchanged (default: False). Use as an escape hatch when you need the full propagation chain or raw attribute payload (debug / inspection). WARNING: brings back token-bloat for nested-group targets — prefer result_fields / result_attribute_keys for targeted control.
entity_idNo
ws_commandNoAdvanced escape hatch: send a raw one-shot Home Assistant WebSocket command that is NOT a registered service (e.g. 'repairs/ignore_issue' to dismiss a Repairs issue). When set, omit domain/service and the other service params; put the command's parameters in data. Streaming/two-phase and service-invoking commands (call_service, execute_script) are rejected.
result_fieldsNoProject each record in 'result' to only these top-level keys (e.g. ['entity_id', 'state']). Mirrors ha_get_state's fields=. Setting this DISABLES default compaction — no entity-id filter, no metadata strip — and applies the explicit projection instead.
return_responseNo
result_attribute_keysNoProject each record's 'attributes' dict to only these keys (e.g. ['brightness', 'rgb_color']). Mirrors ha_get_state's attribute_keys=. Setting this DISABLES default compaction. Requires 'attributes' to be present in result_fields (or result_fields=None).

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The annotations already declare destructiveHint=true, so the burden on the description is lower. The description adds significant behavioral context: wait behavior, result compaction, verbose escape hatch, and WebSocket command limitations. It matches the annotations and provides concrete details an agent needs.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is detailed but well-organized with headings, code examples, and bullet points. It is front-loaded with the core purpose and basic usage. While slightly long, every section adds value.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's complexity (10 parameters, multiple escape hatches, output schema exists), the description covers essential aspects: basic usage, common patterns, result formatting, and advanced WebSocket commands. It is complete enough for an agent to use effectively.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is only 40%, but the description compensates well. It explains the domain.service pattern with examples, clarifies parameters like entity_id and data usage in context, and details the behavior of parameters like verbose, result_fields, and ws_command beyond the schema descriptions.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description explicitly states 'Execute Home Assistant services to control entities and trigger automations' and identifies itself as 'the universal tool for controlling all Home Assistant entities.' This clearly distinguishes it from sibling tools which are more specific (e.g., ha_get_state, ha_search).

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides explicit guidance on when to use this tool: 'Common patterns: Use ha_get_state() to check current values before making changes. Use ha_search() to find correct entity IDs.' It also explains when to use the WebSocket command escape hatch for operations like dismissing repairs, and notes that streaming/two-phase commands are rejected.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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