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

Adds substantial context beyond annotations: non-idempotent re-add behavior (calling again adds again), partial failure handling (skipped items listed in messages), 20 kg parcel limit, error when nothing is found, and no charge until checkout. Annotations already declare idempotentHint=false and destructiveHint=false, so this adds rich extra detail without contradicting them.

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-loaded with the primary use case, then constraints and edge cases. Dense but each sentence carries actionable information. Slightly long, but appropriate for a tool with non-obvious side effects and partial-failure semantics.

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?

Covers prerequisites, scoping, quantity behavior, pricing, accumulation onto existing basket, partial failure, error condition, repeat-call behavior, and the fact that nothing is charged. An output schema exists, so return payload detail is not needed. Complete for the complexity level.

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 baseline is 3, but the description adds real semantics: only_ids is scoped to 'from that order' and otherwise every product is added in original quantity, and order_number must originate from my_orders. This clarifies intent beyond the schema's terse parameter docs.

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 (buy again) and resource (an earlier teas.co.uk order), and distinguishes itself from sibling add_to_basket by being order-driven rather than product-driven. An agent can route correctly without opening schemas.

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?

Explicitly says when to use (signed-in customer reordering a past order) and points to my_orders as the prerequisite for discovering order_number. It also clearly states when not to rely on it (no charge until payment on teas.co.uk).

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