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by Koredotcom
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TypeScript
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debug_get_span_tree

Trace failures and understand agent behavior by retrieving a hierarchical span tree of execution flow from live sessions.

Instructions

[Arch Debug] Arch connects to live sessions, traces failures, and inspects execution state. Get hierarchical span tree showing execution flow. Useful for understanding agent behavior.

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": "debug_get_span_tree"
  }
}

Input Schema

NameRequiredDescriptionDefault
flatNoReturn as flat list with depth info instead of tree
sessionIdNoSession ID (uses active session if not specified)

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.5.0

TDQS

C2.9/5.0
Behavior2/5

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

No annotations are provided, so the description carries the full burden for behavioral disclosure. It does not state whether the tool is read-only, requires authentication, has rate limits, or produces side effects. The description focuses on the output nature (span tree) but omits any operational caveats or error scenarios.

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 concise, with three sentences. The first sentence provides broad Arch context, the second states the tool's action, and the third gives a general use case. It is front-loaded with the specific action clearly stated. Minor waste in the generic Arch context sentence, but overall efficient.

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?

For a simple tool with only two optional parameters and no output schema, the description is adequate for basic invocation. However, it does not explain what constitutes a 'span tree' beyond 'execution flow', nor does it describe the return structure or any potential pitfalls. The lack of output schema places more burden on the description to clarify the result format, which it only partially does.

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

Parameters3/5

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

Schema description coverage is 100%: both 'flat' and 'sessionId' have descriptive text in the schema. The tool description adds no additional meaning beyond what the schema provides, so the baseline score of 3 is appropriate given the schema's completeness.

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

Purpose4/5

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

The description states a specific verb and resource: 'Get hierarchical span tree showing execution flow.' This clearly indicates the tool's purpose. It doesn't explicitly differentiate from similar siblings like debug_get_flow_graph, but the mention of 'span tree' provides enough specificity for basic distinction.

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

Usage Guidelines2/5

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

The description provides no guidance on when to use this tool versus alternatives. The phrase 'Useful for understanding agent behavior' is a vague benefit, not a usage condition or exclusions. No sibling alternatives are mentioned, leaving the agent to infer suitability from the generic context.

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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