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

Annotations only say this is a non-read-only, non-destructive, closed-world mutation. The description adds genuine behavioral detail beyond that: merge semantics for supplied fields, the fact that unavailableOutletIds REPLACES rather than appends (the destructive part of an otherwise non-destructive annotation), the [] reset escape hatch, and a server-side refusal condition. No contradiction with the annotations.

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?

Front-loads the operation and its editable fields, then immediately states the merge rule, then the exception-list semantics, then the refusal caveat. Each sentence carries distinct, non-redundant information with no filler.

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 an 8-parameter mutation with no output schema and only 50% schema coverage, the description covers the update contract, the risky replace semantics, and the failure mode well. The remaining gap is sortOrder/defaultQuantity, whose behavior an agent must infer or find in the reorder sibling 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?

Schema description coverage is 50%, and the description clarifies isDefault ('pre-selected') and outlet availability ('where it is sold') while restating the replace behavior already documented on unavailableOutletIds and price. sortOrder and defaultQuantity remain undocumented in both schema and description, so the description only partially compensates for the coverage gap.

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 and narrow resource ('Change one choice') and then enumerates exactly which attributes can be changed (name, price, pre-selection, outlet availability). This clearly separates it from hub_add_modifier_choice and hub_delete_modifier_choice, though it never names those siblings explicitly.

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?

Gives strong context for how to call it: it is a partial update, so omitted fields are left untouched, and it warns that unselling a choice can be refused by category rules. It does not explicitly route the agent to siblings such as hub_reorder_modifier_choices, so it stops short of full when/when-not/alternatives guidance.

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