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

The annotations already declare destructiveHint=true and readOnlyHint=false, indicating mutation. The description adds that icon and color can be cleared with null, which is a behavioral nuance not obvious from the schema alone. It also mentions built-in categories are immutable. However, it does not disclose the exact effects of changing a category (e.g., whether it cascades to existing transactions), which would be valuable. Since annotations already cover the destructive nature, the description adds useful but not exhaustive context.

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 concise and well-structured, with two sentences. The primary purpose is front-loaded, followed by a key constraint (system categories), and then a pointer to where IDs come from. Every sentence adds value without redundancy. It is a model of efficient, useful description.

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?

The output schema exists, so no need to explain return values. The description covers the essential usage: what fields can be modified, the null-clearing behavior, the immutability of system categories, and how to obtain IDs. An agent has enough information to call this tool correctly. The idempotentHint suggests repeated calls are safe, which is consistent. The description is complete for this tool's complexity.

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?

The schema coverage is 50% (only id and icon have descriptions, but name and color are missing). The description compensates by explaining the semantics of icon and color (they can be cleared with null) and provides domain context (category IDs come from list_categories, and system categories can't be changed). This adds meaning beyond the schema for at least the 'name' and 'color' parameters, which otherwise have no textual explanation. The description fully covers the missing schema details.

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 clearly states it renames a category or changes its icon or color, specifying the exact resource ('category') and the actions. It also highlights the special behavior of clearing icon/color with null, and distinguishes from siblings by noting built-in system categories cannot be changed and that IDs come from list_categories. This is a specific and differentiating purpose.

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 implies when to use it: when you need to edit an existing category, as opposed to creating one (create_category) or deleting it (delete_category). It also notes that system categories like Transfer cannot be changed, which is an explicit exclusion that guides usage. However, it does not explicitly name the alternative tools or state 'use instead of...' but the context is clear enough for a knowledgeable agent.

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