Firefly III MCP Server

Create Firefly III Category

firefly_create_category

Create transaction categories in Firefly III to classify expenses and income. Specify names and optional notes to organize financial data and track budgets.

Instructions

Create a new transaction category.

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": {
      "name": "<name>"
    },
    "name": "firefly_create_category"
  }
}

Input Schema

Name	Required	Description	Default
`name`	Yes	Category name
`notes`	No	Optional notes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.1Apr 7, 2026

TDQS

C2.9/5.0

Behavior2/5

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

While annotations declare the safety profile (readOnlyHint: false, destructiveHint: false), the description adds no behavioral context. It omits critical information implied by idempotentHint: false regarding duplicate creation, does not explain validation rules, success responses, or whether category names must be unique within Firefly III.

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?

The four-word description is extremely concise with no redundancy. However, it is arguably underspecified rather than efficiently minimal, as it wastes no words but also fails to include necessary behavioral warnings.

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

Completeness3/5

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

For a simple two-parameter creation tool with complete schema documentation and comprehensive annotations, the description is minimally adequate. However, given the non-idempotent nature of the operation, it lacks important context about duplicate handling that would be necessary for safe agent operation.

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?

With 100% schema description coverage ('Category name' and 'Optional notes'), the schema adequately documents parameters. The description adds no additional semantic value regarding parameter usage, but the baseline score of 3 is appropriate given the schema completeness.

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?

The description uses the specific verb 'Create' and resource 'transaction category', clearly identifying the tool's function. However, it does not distinguish from sibling tools like 'firefly_update_category' or explain what distinguishes a category from other Firefly III entities like budgets or tags.

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?

The description provides no guidance on when to use this tool versus alternatives. It fails to mention that 'idempotentHint' is false, meaning duplicate calls create multiple categories, and does not advise checking 'firefly_list_categories' first to avoid duplicates.

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