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

The destructiveHint=true annotation already announces that this is a write with destructive potential, and 'MUTATES Autumn billing data' is consistent with that. The description adds the REST endpoint as useful context, but says nothing about idempotency of entity_id, required API permissions, or error behavior when the entity already exists — which is the information an agent actually lacks for a mutation.

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?

A single compact sentence with the mutation warning front-loaded before the resource explanation and the endpoint. Every clause carries information; nothing is padded.

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 5-parameter mutation with a nested, unconstrained billing_controls object and no output schema, the definition covers identity and endpoint but not outcomes. An agent still does not know what the call returns or what happens on duplicate entity_id, leaving a meaningful gap for a write 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 100%, so all five parameters including customer_id, entity_id, feature_id, name and billing_controls are already documented in the schema. The description's mention of 'under a customer, tied to a feature' largely restates the schema and adds no format, constraint, or shape detail — notably none for the free-form billing_controls object.

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 resource ('creates an entity') plus the domain relationships — under a customer, tied to a feature — and gives the backing endpoint POST /v1/entities.create. The create verb plus the '(e.g. a seat)' example clearly separates it from autumn_get_entity and autumn_list_entities in the sibling set.

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 (provisioning a per-seat entity against a feature for a known customer) but never states it explicitly. There is no guidance on preconditions such as looking up the customer first via autumn_get_customer, no mention of what happens if the entity_id already exists, and no named alternative.

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