rootcause-mcp

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rc_ask_why

Drill down into root causes by answering 'Why?' repeatedly, building a WhyChain up to five levels deep for systematic root cause analysis.

Instructions

Ask 'Why?' to drill down into root causes using 5-Why analysis. Creates or extends a WhyChain for the session. Each call goes one level deeper (up to 5 levels). This is the CORE tool for systematic root cause reasoning.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "session_id": "<session_id>",
      "answer": "<answer>"
    },
    "name": "rc_ask_why"
  }
}

Input Schema

Name	Required	Description
`session_id`	Yes	The session ID
`answer`	Yes	The answer to 'Why?'. This becomes the basis for the next question. Example: 'Because the nurse miscalculated the dose'
`parent_node_id`	No	Optional: ID of parent node to branch from. If not provided, continues from the last node or creates first Why.
`evidence`	No	Supporting evidence for this answer (optional)
`initial_problem`	No	The initial problem statement. Required only for the FIRST Why in a chain.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0May 26, 2026

TDQS

A4.3/5.0

Behavior4/5

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

With no annotations provided, the description takes on the full burden. It discloses the key behavioral aspect: each call goes one level deeper up to 5 levels. It does not describe the output format or what happens after the 5th level, but overall it is fairly 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 three sentences, each earning its place: first states purpose, second explains behavior with constraints, third emphasizes importance. No fluff.

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

Completeness3/5

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

Given no output schema and no annotations, the description should hint at the return value. It does not describe what the tool returns after each call. It covers the reasoning flow well but omits output expectations, making it slightly incomplete.

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 coverage is 100%, so the schema already documents each parameter. The description adds value by explaining the role of 'initial_problem' (required only for first Why) and the default behavior of 'parent_node_id', which clarifies usage beyond the schema.

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 the action ('Ask Why?'), the resource ('drill down into root causes using 5-Why analysis'), and distinguishes from siblings by labelling itself 'the CORE tool for systematic root cause reasoning.'

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 explains that each call goes one level deeper (up to 5 levels) and that it creates or extends a WhyChain, giving clear context for when to use it. However, it does not explicitly mention when not to use it or compare to alternative tools like rc_add_cause or rc_get_why_tree.

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