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

With annotations only saying readOnlyHint=false/openWorldHint=true, the description supplies the critical non-obvious behaviors: 10-minute TTL, single-use token, no stock reservation with decrement deferred to place_order, and fail-fast on out-of-stock. It also flags the offer_id variant that 'consumes nothing' and returns session_token:null, which an agent could easily mis-handle without this note.

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 core action and token contract, then supports it with a numbered rationale list. Slightly dense with markdown emphasis and parentheticals, but nearly every clause carries actionable information (TTL, single-use, liability scope, stock 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?

Without an output schema, the description still explains the returned session_token, its lifetime, and its single-use constraint, plus what a null token means for the offer_id path. Together with the ordering relative to place_order, an agent has everything needed to call and consume the result correctly.

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 api_key, offer_id, quantity, and product_id are already documented in the schema, and the description largely restates the token/offer rules rather than adding new parameter semantics. It does reinforce the subtle offer_id rule ('pass this same offer_id, never the null'), but this is duplication rather than net-new meaning. 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?

Opens with a specific verb+resource and its position in the flow: 'Lock the displayed price BEFORE webaz_place_order — returns session_token'. It explicitly delineates what the tool is NOT ('Price-lock ONLY … does NOT reserve/hold stock'), which cleanly separates it from place_order and from any stock-holding sibling.

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 both sides of the decision: 'USE THIS for EVERY purchase' with four enumerated reasons, plus the explicit exclusion 'Skipping is allowed but the agent then carries price-drift risk itself.' The prerequisite ordering (before webaz_place_order) and the follow-up (pass session_token to place_order) are stated.

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