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QGIS MCP Server

QGIS MCP Server

by LuiccianDev
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Hybrid

Add Field

add_field

Add a new attribute field to a QGIS vector layer, specifying field name, type, and optional length or precision for structured data storage.

Instructions

Add a new field to a vector layer. field_type: 'string', 'int', 'double', 'bool', 'date', 'datetime'.

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": {
      "layer_id": "<layer_id>",
      "field_name": "<field_name>",
      "field_type": "<field_type>"
    },
    "name": "add_field"
  }
}

Input Schema

NameRequiredDescriptionDefault
lengthNo
layer_idYes
precisionNo
field_nameYes
field_typeYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

C2.9/5.0
Behavior1/5

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

No annotations are provided, and the description does not disclose behavioral traits such as what happens if the field already exists, if the layer is not a vector layer, or if the field type is invalid. The agent has no information about side effects or requirements.

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 extremely short with two sentences, no fluff. The core action and important enum values are front-loaded. Every word earns its place.

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 5 parameters, no output schema, and no annotations, the description is incomplete. It fails to explain return values, constraints (e.g., required formats, uniqueness), or error conditions, making it insufficient for an agent to use confidently.

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%, so the description must add meaning. It only explains the field_type parameter with a list of values, but does not describe layer_id, field_name, length, or precision, leaving most parameters undefined.

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 description clearly states 'Add a new field to a vector layer' with a specific verb and resource, and lists the allowed field types, distinguishing it from sibling tools like delete_field and rename_field.

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

Usage Guidelines2/5

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

No guidance on when to use this tool versus alternatives (e.g., delete_field, rename_field) or what prerequisites are needed (e.g., layer must be editable, field_name must be unique).

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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