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

readOnlyHint=true already declares the safety profile, and the description reinforces it with 'Changes nothing', so no contradiction. It further discloses what the response contains (item, print, shipping, tax, retail totals) and the underlying endpoint (POST /orders/estimate-costs), adding value beyond the annotation.

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?

Three short, front-loaded sentences with no filler; the key constraint (no order created) and the sibling reference are stated up front.

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, the description usefully enumerates the cost categories returned, and the nested item/recipient shapes are fully covered by the schema. It does not mention pagination or error/permission behavior, but for a read-only estimate that is a minor gap.

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 coverage is 100%, so all five parameters are already documented in the schema; the description only adds the cross-reference that items share the draft-order shape. That is useful but marginal, so 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?

The description gives a specific verb (price/estimate) and resource (order costs) and explicitly negates the write path with 'WITHOUT creating it'. It enumerates the cost components (item, print, shipping, tax, retail totals), so an agent can distinguish it from printful_create_draft_order 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?

It states the tool changes nothing and cross-references siblings ('Same item shape as printful_create_draft_order', shipping id from printful_calculate_shipping_rates), which tells the agent when to pick this over the draft-order tool. It stops short of spelling out exclusions or failure conditions.

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