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p21

p21

by mocchan0221
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Local

Find printers

p21_scan
Read-only

Scans for available label printers over Bluetooth Classic, serial, and BLE in about 5 seconds so you can choose a device to print labels.

Instructions

Search for P21 printers (paired Bluetooth Classic devices, serial ports, BLE). Takes ~5 s.

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": "p21_scan"
  }
}

Input Schema

NameRequiredDescriptionDefault
bleNo

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

B3.1/5.0
Behavior3/5

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds a genuinely useful latency estimate (~5 s) and the scope of scanning, but says nothing about whether the call blocks, what permission prompts it may trigger, or how many results come back.

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?

Two compact sentences with the purpose front-loaded and the latency caveat second; nothing is padded. Slightly more detail on the parameter would have fit without hurting brevity.

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?

With one optional parameter and no output schema, the description should explain what a scan returns (a device list? handles to pass to p21_print?) and what the `ble` flag does. Neither is covered, so an agent knows the tool's purpose but not its result shape or how to chain it into p21_print.

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?

Schema description coverage is 0% for the single `ble` boolean (default true), so the description carries the burden. It mentions BLE in the list of scanned transports, which hints at the parameter's role, but never states that `ble=false` restricts the scan to Bluetooth Classic and serial, or that omitting it defaults to true.

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?

States a specific verb (search/scan) and resource (P21 printers) and enumerates the transport types covered (Bluetooth Classic, serial ports, BLE), which clearly separates it from p21_print or p21_status. It does not explicitly name a sibling or the ordering relationship, but the resource is distinct enough that an agent can tell them apart.

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?

Discovery-before-print is only implied by the verb 'search'; there is no explicit statement such as 'call this before p21_print to obtain a device handle' or any exclusion. The ~5 s note helps an agent decide whether to block, but the when/when-not guidance is left to inference.

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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