stm32-stlink-mcp

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Write a core register

register_write

Write a value to a core register (e.g., r0, pc, sp) on STM32 microcontrollers via ST-LINK, enabling direct register modification for debugging and testing.

Instructions

Writes a value to a named core register via gdb's -gdb-set $<register>=<value>.

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": {
      "sessionId": "<sessionId>",
      "register": "<register>",
      "value": "<value>"
    },
    "name": "register_write"
  }
}

Input Schema

Name	Required	Description
`value`	Yes	Value expression, e.g. '0x08000200' or '42'
`register`	Yes	Register name, e.g. 'r0', 'pc', 'sp'
`sessionId`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Aug 21, 2026

TDQS

B3.3/5.0

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. It states the write action and the underlying gdb command, but does not disclose side effects, session requirements, error behavior, or whether the operation is reversible. For a mutation tool, this is minimal disclosure.

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 a single, front-loaded sentence that immediately states the action and mechanism. No unnecessary words, perfectly concise.

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

Completeness2/5

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

For a tool with no output schema and no annotations, the description is too sparse. It fails to mention when to use it, any required preconditions (like an established debug session), or what happens after the write (e.g., confirmation, potential failure modes). The agent gets only the basic write intent.

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

Parameters2/5

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

The schema covers two of three parameters with descriptions (value and register), but sessionId is undocumented. The description adds no extra parameter meaning beyond referencing the gdb command, and does not clarify what sessionId refers to or how it relates to the session context.

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 title and description clearly state the tool writes a value to a core register via gdb's `-gdb-set` command. It uses a specific verb (writes) and resource (core register), and distinguishes from siblings like register_read and memory_write by specifying the register access path.

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?

The description implies usage for writing registers but does not mention when to use versus alternatives like register_read or memory_write, nor does it state exclusions or prerequisites (e.g., needing an active debug session). It provides no explicit guidance on context.

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