Firefly III MCP Server

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

Annotations indicate idempotentHint=true and destructiveHint=false, establishing safety. The description adds crucial behavioral context that this is a partial update operation ('Only provide the fields you want to change') and mandates a read-before-write workflow, which is essential for correct usage.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences with zero waste. The first sentence states the action and constraint; the second provides the workflow prerequisite. Information is front-loaded and every word earns its place.

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

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

For a 10-parameter update tool with safety annotations covering idempotency and destructiveness, the description adequately explains the partial update pattern and prerequisite workflow. It appropriately omits return value details (no output schema exists), though it could briefly mention success/failure signaling for full completeness.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

While the schema has 100% description coverage, the description adds essential semantic meaning by clarifying that parameters are optional partial updates ('Only provide the fields you want to change'). This explains the PATCH-like behavior that isn't evident from the schema alone, where all non-id fields appear optional but the semantic intent isn't stated.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with the specific action 'Update an existing transaction', clearly identifying both the verb (update) and resource (transaction). The word 'existing' effectively distinguishes it from the sibling firefly_create_transaction tool.

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

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

The description provides explicit workflow guidance: 'First use firefly_get_transaction to retrieve the current values, then pass only the changed fields here.' This establishes the prerequisite step and partial update pattern. However, it lacks explicit 'when not to use' guidance (e.g., contrasting with delete_transaction or create_transaction).

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