Resources

MCP resources provide structured, read-only data that clients can access without executing tools. mcpyvisa exposes two static resources: the AR488/Prologix command reference and (when pymeasure is installed) the list of instruments with validated driver support.

---

visa://protocol/commands

URI: visa://protocol/commands

Returns the full AR488/Prologix ++ command reference as a JSON document. This resource is static — it does not require a connected backend and is available immediately on server startup.

This is useful for LLMs that need to construct raw ++ commands or understand the underlying protocol without having to consult external documentation.

Reading the resource

result = await client.read_resource("visa://protocol/commands")

Response structure

The response is a JSON object with three top-level keys:

{
  "prologix_commands": {
    "++addr [N]": "Show or set current GPIB address (1-30)",
    "++auto [0|1|2|3]": "Auto-read mode: 0=off, 1=prologix, 2=on-query, 3=continuous",
    "++clr": "Send Selected Device Clear (SDC) to addressed device",
    "++eoi [0|1]": "Enable/disable EOI assertion on last byte",
    "++eor [0-7]": "Set EOR char: 0=CRLF 1=CR 2=LF 3=None 4=LFCR 5=ETX 6=CRLF+ETX 7=SPACE",
    "++eos [0-3]": "Set end-of-send character (0=CRLF, 1=CR, 2=LF, 3=None)",
    "++eot_enable [0|1]": "Enable/disable appending EOT character on EOI detection",
    "++eot_char [N]": "Set EOT character (ASCII 0-255)",
    "++ifc": "Assert Interface Clear for 150us -- become Controller-In-Charge",
    "++llo [all]": "Local Lockout -- disable front panel on instrument(s)",
    "++loc [all]": "Go To Local -- re-enable front panel on instrument(s)",
    "++mode [0|1]": "Set interface mode: 0=device, 1=controller",
    "++read [eoi|N]": "Read from bus until EOI, char N, or timeout",
    "++read_tmo_ms [N]": "Set read timeout in milliseconds (1-32000)",
    "++rst": "Reset the controller",
    "++savecfg": "Save configuration to NVS flash",
    "++spoll [N]": "Serial poll address N (or current address)",
    "++srq": "Return SRQ line state (0=unasserted, 1=asserted)",
    "++status [N]": "Set/get status byte for device mode",
    "++trg [N ...]": "Send Group Execute Trigger to address(es)",
    "++ver [real]": "Show firmware version string",
    "++verbose [0|1]": "Enable/disable human-readable output"
  },
  "extended_commands": {
    "++allspoll [N ...]": "Serial poll multiple addresses, returns addr:status pairs",
    "++findlstn": "Find all listeners on the bus (returns space-separated addresses)",
    "++findrqs [N ...]": "Find device requesting service (returns SRQ:addr,status)",
    "++dcl": "Send Universal Device Clear to all devices",
    "++default": "Reset to factory default configuration",
    "++id name [S]": "Show/set interface name (max 15 chars)",
    "++id serial [N]": "Show/set interface serial number (max 9 digits)",
    "++id verstr [S]": "Show/set custom version string (max 47 chars)",
    "++idn [0|1|2]": "Enable *IDN? response: 0=off, 1=name, 2=name+serial",
    "++macro [N] [set|del]": "List/run/edit/delete macros (0-9, 128 bytes each)",
    "++ppoll": "Conduct parallel poll (returns response byte)",
    "++prompt [0|1]": "Show/hide command prompt",
    "++ren [0|1]": "Assert/deassert Remote Enable",
    "++repeat N ms cmd": "Repeat a command N times with ms delay",
    "++setvstr [S]": "Set custom version string (alias for ++id verstr)",
    "++srqauto [0|1]": "Auto serial poll on SRQ assertion",
    "++tmbus [N]": "Bus settling delay in microseconds (0-30000)",
    "++ton [0|1]": "Talk-only mode",
    "++xdiag mode byte": "Bus diagnostics: mode 0=data, 1=control"
  },
  "notes": {
    "gpib_addresses": "Valid range 0-30. Address 0 is typically the controller.",
    "scpi_queries": "Commands ending with '?' expect a response -- use instrument_query.",
    "scpi_commands": "Commands without '?' set parameters -- use instrument_write.",
    "common_scpi": [
      "*IDN? -- Identify instrument",
      "*RST -- Reset to power-on defaults",
      "*CLS -- Clear status registers",
      "*ESE N -- Set event status enable register",
      "*ESR? -- Read event status register",
      "*OPC -- Operation complete",
      "*OPC? -- Operation complete query",
      "*SRE N -- Set service request enable register",
      "*STB? -- Read status byte",
      "*TST? -- Self-test",
      "*WAI -- Wait for pending operations"
    ]
  }
}

Tip

The notes.common_scpi array lists IEEE 488.2 mandatory commands that nearly all modern instruments support. These are a reliable starting point when working with an unfamiliar instrument.

---

visa://pymeasure/supported

URI: visa://pymeasure/supported

Returns a JSON array of instruments that have pymeasure driver support. This resource is only available when pymeasure is installed (pip install mcpyvisa[pymeasure]).

Use this to quickly check which instruments on the bench can use the validated instrument_inspect / instrument_get / instrument_set / instrument_call tools instead of raw SCPI.

Reading the resource

result = await client.read_resource("visa://pymeasure/supported")

Response structure

[
  {
    "catalog_id": "keithley-2400",
    "module": "pymeasure.instruments.keithley",
    "class_name": "Keithley2400"
  },
  {
    "catalog_id": "hp-34401a",
    "module": "pymeasure.instruments.hp",
    "class_name": "HP34401A"
  },
  {
    "catalog_id": "keithley-2000",
    "module": "pymeasure.instruments.keithley",
    "class_name": "Keithley2000"
  }
]

Each entry maps a catalog identifier (used internally for IDN matching) to the pymeasure module and class that provides the validated driver.

Note

This resource is static — it lists all instruments that mcpyvisa can support, not just the ones currently on the bus. Cross-reference with discover_instruments to see which of your bench instruments have driver support.