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

Goes beyond the readOnly/idempotent annotations by disclosing freshness semantics ('prices and stock are read again on every call') and error behavior ('an unknown basket_id, or a basket never filled, comes back as an empty basket ... rather than an error'). Those are exactly the non-obvious traits an agent needs to interpret an empty result correctly.

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 purpose, then parameters, then edge-case behavior, then sibling routing. Dense but every sentence carries information; it runs slightly long for a one-parameter read tool, which keeps it from a full 5.

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?

An output schema exists, so return values need no explanation, and the description still covers freshness, the empty-basket edge case, and the alternative tools for mutation. Nothing an agent needs to call this correctly is missing.

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 already 100%, so basket_id's meaning is documented structurally. The description adds one genuinely new condition beyond the schema text: pass it only when an earlier basket tool returned one. Otherwise it largely restates the schema, which caps this below a 5.

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 ('show what is in the customer's teas.co.uk basket') plus what it returns (live subtotal, delivery estimate). It is immediately distinguishable from siblings like add_to_basket and update_basket, which are named.

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 explicit routing: use add_to_basket to add, update_basket to change quantities, checkout_link to pay. It also states precisely when to include basket_id and when to omit it, with no ambiguity left to inference.

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