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

Annotations already indicate this is not read-only, and the description confirms a creation side effect. It adds the 'custom category' framing and notes that it returns the created details, but it does not disclose behavior such as duplicate handling, uniqueness constraints, or whether creation can fail. This is adequate but not rich.

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?

The description is compact and well-organized with Args and Returns sections. Every sentence contributes necessary information: the action, the parameter constraints, and the return behavior. There is no filler or redundancy.

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 simple two-parameter create tool, the description covers the essential inputs and return value. It could be slightly more complete by specifying the shape of the created category details or error conditions, especially since no output schema exists, but it is sufficiently complete for correct invocation in most cases.

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?

Schema description coverage is 0%, so the description must carry the parameter semantics. It does so fully: name is limited to 50 characters, category_type is restricted to 'income' or 'expense', and the default is 'expense'. This adds meaningful meaning beyond the raw schema, which only lists string types and a default.

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 states a specific action and resource: 'Create a new custom category.' This clearly distinguishes it from sibling tools like update_category, delete_category, and list_categories, and from other create_* tools such as create_tag or create_transaction.

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 no guidance on when to use this tool versus alternatives, such as when a custom category is appropriate versus using existing categories or creating a tag. There are no stated exclusions, prerequisites, or decision heuristics, leaving the agent to infer usage context.

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