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

Adds substantial context beyond the annotations: continuous per-minute billing from creation until stop/destroy, the required instances:write scope, and the asynchronous lifecycle detail that the caller must poll get_instance until status is running (1-5 minutes). None of this is discoverable from the structured fields, which is exactly what the description should carry.

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?

Five short sentences, front-loaded with purpose, then cost, then a safety instruction, then permission, then the post-call workflow. No filler and each sentence delivers an operational fact.

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?

With no output schema present, the description correctly supplies the return value ('the response has the instance id') and the follow-up polling procedure. Combined with full schema coverage, an agent has everything needed to invoke and sequence this call.

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 the schema already documents all 8 parameters including enum values, ranges, defaults, and the idempotency_key retry semantics. The description adds no parameter-level syntax or constraints beyond that, so the baseline 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?

States a specific verb and resource ('rents the server of an offer and starts it with a template'), which cleanly separates it from the sibling start_instance (starts an existing instance) and destroy_instance. An agent can identify this as the provisioning/create operation without opening the 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?

Gives prerequisite guidance by naming the upstream tools for its required inputs (offer_id from search_offers, template from list_templates, implicitly), plus the operational rule 'confirm the price with the user first.' It does not explicitly contrast with start_instance for the case where an instance already exists, so it falls short of a full when/when-not statement.

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