get_checkout_preview

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

Annotations already cover the safety profile (readOnlyHint=true, idempotentHint=true, destructiveHint=false). The description adds value beyond them by clarifying that the tip_cents input does NOT alter the cart's stored tip and that no submission occurs, which resolves an ambiguity the annotations alone would not.

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 sentences, front-loaded with the core action, then the return fields, then the explicit non-behavior. No filler or repetition; each sentence earns its place.

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 steps in to name the key return fields (total_cents, preview_hash), which is exactly the gap it should fill. Combined with the annotation-covered safety profile, an agent has enough to invoke it correctly, though cart_id's semantics remain unaddressed.

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 0%, so the description must carry parameter meaning. It does explain tip semantics ('explicit tip', 'does not change cart tip'), which is genuinely useful, but says nothing about cart_id's role or the total_cents/preview_hash relationship to inputs, leaving half the parameters undocumented.

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+resource ('Read current checkout pricing and selected saved payment card') and distinguishes this preview from the mutation sibling place_order by noting preview_hash is 'for place_order'. It is clear and non-tautological, though it does not explicitly contrast with get_cart, which could also be a candidate for reading cart state.

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?

The flow is implied: preview_hash is 'for place_order' and the tool 'does not submit', so an agent can infer this is a pre-submission read step. However, there is no explicit 'call this before place_order' or 'use X instead when Y' instruction, so guidance is implied rather than stated.

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