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start_gcode_interception

Start a real-time G-code interception session for a 3D printer to enforce safety rules such as temperature limits, feedrate caps, and blocked commands before unsafe commands execute.

Instructions

Start a real-time G-code interception session for a printer.

Automatically loads safety-profile-based rules (temperature limits,
feedrate caps, blocked commands) for the printer.  Use
``add_interception_rule`` to add custom rules after starting.

Args:
    printer_name: The printer, as registered in Kiln or by its model
        key (e.g. ``"bambu_a1"``); a model key gives the fullest rule
        set, a nickname Kiln cannot resolve to a model loads generic
        limits and says so in ``coverage_warnings``.

Returns a session ID and initial rule set.

AGENT CONTRACT: when ``coverage_warnings`` is non-empty this session
is running with reduced protection (generic temperature limits, or no
bed-fit rules because the build volume is unknown).  Relay those
warnings to the user verbatim -- do not present the session as fully
protected.  Passing the printer's model key (e.g. "bambu_a1") instead
of a nickname resolves the gap.

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": {
      "printer_name": "<printer_name>"
    },
    "name": "start_gcode_interception"
  }
}

Input Schema

NameRequiredDescriptionDefault
printer_nameYesThe printer, as registered in Kiln or by its model key (e.g. ``"bambu_a1"``); a model key gives the fullest rule set, a nickname Kiln cannot resolve to a model loads generic limits and says so in ``coverage_warnings``.

Output Schema

NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv1.5.1
    • addedInput schema / properties / printer_name / description
      Added value: +"The printer, as registered in Kiln or by its model key (e.g. ``\"bambu_a1\"``); a model key gives the fullest rule set, a nickname Kiln cannot resolve to a model loads generic limits and says so in ``coverage_warnings``."
  2. First observedv0.1.0

TDQS

A4.2/5.0
Behavior4/5

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

Annotations only declare readOnly=false, destructive=false, openWorld=false; the description adds far more: that rules are auto-loaded at session start, that unresolvable printers silently fall back to generic limits, and that the response carries coverage_warnings. Calling this a read-only-ish session start with 'no destructive actions' would be odd, but the annotations already cover that adequately, so this adds useful context beyond them. It does not mention concurrency limits on sessions, which is the remaining behavioral gap.

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?

Purpose, automatic behavior, follow-up tool, Args, return, and the agent contract are ordered sensibly with the key scoping fact front-loaded. The only waste is the Args paragraph duplicating the schema description word for word.

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?

An output schema exists, so return values need not be enumerated, yet the description still names what comes back (session ID, rule set). It covers the degraded-protection case and the required agent behavior for coverage_warnings, leaving nothing an agent needs to call and report on correctly.

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 coverage is 100% and the description's Args block repeats the schema's parameter text almost verbatim, adding no new syntax or constraints. With a single required, fully documented parameter, 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 ('Start a real-time G-code interception session for a printer') and immediately scopes what the session loads ('safety-profile-based rules: temperature limits, feedrate caps, blocked commands'). It is clearly distinct from siblings like add_interception_rule, stop_gcode_interception, and get_interception_status.

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?

Explicitly routes follow-up customization to add_interception_rule after starting, and explains the model-key vs nickname choice with its consequence. It stops short of stating when to prefer this over adjacent tools such as load_safety_interception_rules or validate_gcode_safe, so there is no full when/when-not matrix.

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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