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

Goes well beyond the annotations (destructiveHint=true, idempotentHint=false) by spelling out the mutation contract: partial updates touch only supplied keys, null clears an optional field, empty string clears text but not numbers or closed lists, and required fields can be changed but not cleared. That is exactly the behavioral detail an agent needs to avoid unintentionally wiping a water recipe's mineral figures.

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?

Purpose is front-loaded in the first clause, and the following sentences are dense but each one carries a distinct, necessary rule about clearing and omission. No filler or restatement of the title.

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 mutation tool with annotations covering safety and a present output schema, the description covers the update contract, clearing rules and the reason-only case. It omits permission/error expectations, but nothing that would cause an agent to mis-invoke the tool.

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?

With 67% schema coverage the description carries real weight: it defines the semantics of the nested fields object (which keys change, how to clear values) rather than just listing them, and clarifies the reason parameter's effect. The water_id parameter is already well documented in the schema, so the description adds little there.

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?

States a specific verb (correct/update) and resource (a registered water) and enumerates the mutable surface — name, type, mineral figures, notes. The word 'registered' implicitly separates it from register_water, so an agent can route correctly without opening a schema.

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?

Usage is implied by the partial-update semantics ('only the keys you send change') and the note that fields may be omitted when only reason is sent, which tells the agent this is an edit-existing-record tool. However, it never names an alternative (register_water, delete_shot-style removal, list_waters for lookup) or states prerequisites such as needing a valid water_id from list_waters beyond the schema's own note.

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