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UDS Toolbox

by com.udslib
OverviewDiscussionsAdmin

Decode UDS message

decode_uds
Read-onlyIdempotent

Decode a UDS (ISO 14229-1) PDU from hex: request, positive or negative response. Names the service, sub-function (and suppressPosRsp bit), DID/RID/address fields, and for negative responses the NRC with meaning and typical cause. Unknown SIDs and NRCs are labelled, not rejected.

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": {
      "hex": "<hex>"
    },
    "name": "decode_uds"
  }
}

Input Schema

NameRequiredDescriptionDefault
hexYesPDU bytes, e.g. "7F 34 78" or "0x22 0xF1 0x90" (no ISO-TP header).
directionNoOptional hint to disambiguate.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

A4.1/5.0
Behavior4/5

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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower. The description adds real behavioral value: it enumerates what gets resolved (service, sub-function, suppressPosRsp bit, DID/RID fields, NRC with meaning and typical cause) and discloses graceful handling of unknown SIDs/NRCs (labelled, not rejected).

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?

Three tightly packed sentences with zero filler; the core action is front-loaded and each clause conveys distinct decoding behavior. Nothing is redundant with the title or annotations.

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

Completeness5/5

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

There is no output schema, so the description must carry the return-value burden, and it does by enumerating every field returned for request, positive and negative responses. An agent has everything needed to call and interpret the tool.

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% and both parameters (hex, direction) are documented there, including accepted byte formats and the enum values. The description adds no syntax or format 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+resource: decode a UDS (ISO 14229-1) PDU from hex, covering request, positive and negative responses. This clearly separates it from the sibling build_uds_request (construction) and decode_dtc/decode_isotp (different protocol layers).

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

Usage Guidelines3/5

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

Usage is implied by the decode framing and the schema note that input has no ISO-TP header, which routes an agent toward decode_isotp for framing. However, the description never explicitly states when to use this over siblings or that direction is only an optional disambiguation hint.

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

All UDS Toolbox toolsInspect
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