TxWhy

Diagnose a failed Solana transaction

diagnose_transaction

Explains why a transaction that landed on mainnet failed: the exact failing instruction in the call tree, the named error, its cause, and how to fix it. Read-only and fast. Use repair_transaction when you want a working transaction back.

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": {
      "signature": "<signature>"
    },
    "name": "diagnose_transaction"
  }
}

Input Schema

Name	Required	Description	Default
`signature`	Yes	Transaction signature or explorer URL.

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 8, 2026

TDQS

A4/5.0

Behavior3/5

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

No annotations are provided, so the description carries the full burden. It usefully discloses a read-only, fast profile and the prerequisite that the transaction actually landed on mainnet, but says nothing about auth requirements, rate limits, or behavior for pending/never-landed signatures.

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?

Two tight sentences with zero filler; the capability and its outputs are front-loaded, and the routing hint to repair_transaction is placed last where it belongs.

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?

With no output schema, the description does the work of describing what comes back (failing instruction, error name, cause, fix), which is the right call. The remaining gap is behavioral: an agent still lacks auth/rate-limit context that annotations would normally supply.

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?

Only one parameter and the schema already documents it fully (100% coverage), including the explorer-URL alternative form. The description adds no format or syntax detail beyond the schema, so the baseline 3 applies.

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?

States a specific verb and resource (diagnose a failed transaction) and enumerates the exact outputs: failing instruction in the call tree, named error, cause, and fix. It also names the sibling it is not (repair_transaction), so an agent can separate the diagnostic path from the repair path without reading schemas.

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?

Gives a clear triggering condition (a transaction that landed on mainnet and failed) and explicitly routes to repair_transaction when the goal is a working transaction. It does not, however, address how it differs from the other close sibling, explain_error, leaving some selection ambiguity.

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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