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

Annotations already declare readOnly=false, idempotent=false, destructive=false and openWorld=false, so safety is covered. The description adds a genuinely useful piece of information the annotations lack: the required write scope. It does not disclose whether name must be unique, whether the new category is returned, or what happens on duplicates.

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 short sentences, no filler, with the action stated first and the permission requirement second. Nothing could be trimmed without losing information.

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 three-parameter create tool with full schema coverage and no output schema, this is close to sufficient. The remaining gap is that it never says how the created category is identified in the response or how it relates to the sibling bulk_create.

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 100% – name, is_active and parent_id are each documented in the schema with type, constraints and format. The description adds no parameter meaning beyond that, so the baseline of 3 applies.

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?

Specific verb+resource ("Create a new cost category") that matches the name exactly and is unambiguous against siblings like update_cost_category or delete_cost_category. It does not, however, differentiate itself from bulk_create, which is the one sibling that could plausibly be confused with it.

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?

"Requires cost_categories:write scope" is a prerequisite, not usage guidance. There is no statement of when to use this versus bulk_create, or when to prefer update_cost_category for an existing category. The agent gets a permission note but no selection criteria.

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