hass-mcp-extensions

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get_core_log

Retrieve the Home Assistant core log as plain text. Optionally filter lines with case-insensitive grep and return only the last N lines.

Instructions

Fetch the Home Assistant Core log as plain text.

Replaces the upstream get_error_log tool, which hits /api/error_log — an endpoint removed in HA 2026.5+. This uses the Supervisor proxy /api/hassio/core/logs/latest instead.

Args: tail: If set, return only the last N lines after any grep filtering. grep: Optional case-insensitive substring filter applied per line (e.g. "http.ban" to find failed login attempts).

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "get_core_log"
  }
}

Input Schema

Name	Required	Description	Default
`tail`	No
`grep`	No

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Jun 18, 2026

TDQS

A4.3/5.0

Behavior3/5

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

With no annotations, the description carries full burden. It discloses the action (fetch as plain text) and parameter effects, but does not mention any side effects, rate limits, or limitations (e.g., log size, snapshot nature). It is adequate but not highly transparent.

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

Conciseness5/5

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

The description is concise, front-loading the main purpose, and efficiently explains parameters in two clear paragraphs. No extraneous information.

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 there is an output schema (not shown), the description adequately covers what the tool does and how to use it. It mentions the replacement for get_error_log, which adds context. It is complete for a simple fetch tool, though could note output format or limitations.

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

Parameters5/5

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

The schema has 0% description coverage, but the tool description fully explains both parameters: tail (return last N lines after grep) and grep (case-insensitive substring filter). This adds significant meaning beyond the schema structure.

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 clearly states it fetches the Home Assistant Core log as plain text, and distinguishes itself from the upstream get_error_log tool. The verb 'Fetch' is specific, and the resource is clearly identified.

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

Usage Guidelines4/5

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

The description mentions it replaces get_error_log, implying when to use it for core log retrieval. It also explains the parameters tail and grep, which help with usage. However, it does not explicitly state when to prefer this over other log tools like get_addon_logs or search_addon_logs, though the differentiation is implicit.

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