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

readOnlyHint=true already tells the agent this is a safe read, so the description isn't carrying the safety burden. It adds the underlying endpoint and the customer/timeframe scoping, but says nothing about the response shape, how view_mode changes the result, or any pagination behaviour.

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?

Two short, front-loaded sentences with no filler; the purpose leads and the endpoint reference follows. The endpoint sentence is marginally useful for traceability, though it is the least essential part.

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 and five parameters, the description should at least sketch what comes back (per-customer cost breakdown, how group_by and view_mode alter it). It covers the call but leaves the return value entirely unspecified, which is adequate but thin for a costs-reporting 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 every parameter is already documented in the schema and the baseline of 3 applies. The description adds no syntax, format, or default information beyond the timeframe notion already implied by the name.

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 with scope: 'Get costs incurred by a customer over a timeframe', and pins it to the exact endpoint GET /customers/{customer_id}/costs. The 'customer' qualifier implicitly separates it from the sibling orb_get_subscription_costs, but the description never names that sibling or any other, so differentiation is left to inference.

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?

There is no when-to-use guidance, no indication of when to prefer this over orb_get_subscription_costs or orb_get_customer_credits, and no prerequisites. The 'over a timeframe' phrasing hints at a scoping condition but stops short of telling the agent when this tool is the right choice.

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