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

Annotations only declare a non-readonly, non-idempotent, non-destructive write; the description adds the substantive behavior: tokens are charged in the same call as the claim, no double charge for entitled attitudes, the Starter Octopus is free once per handle ever, and pet_release does not refund. That is exactly the financial/irreversibility context an agent needs before invoking a paid mutation.

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 cost model, then progressively narrower caveats, ending with an example. The opening "Pet Buy." merely restates the title and is dead weight, and the dense clause stacking takes effort to parse, but almost every sentence carries decision-relevant information.

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?

For a paid, one-per-bot mutation with an output schema and full schema coverage, the description covers cost, entitlement, free-starter rules, ownership limits, and non-refundability. Return values are handled by the output schema, so nothing an agent needs to call this safely 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 100%, so the schema already documents all five parameters, but the description adds real meaning: the pick set matches pet_adopt (name, attitude, skin), the special 'starter' attitude costs 0 tokens, and a concrete example call is given. It stops short of explaining the skin_color/skin_pattern interaction, so it is an improvement over baseline rather than exhaustive.

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 ("buy your pet at the merch booth with game tokens") and immediately clarifies scope: "One call pays AND claims the pet." It explicitly distinguishes itself from pet_adopt (free claim) and arena_shop_buy (cosmetics only), so an agent can route correctly without opening the 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?

Gives explicit when-to-use guidance plus the alternatives and the conditions selecting them: use pet_adopt for entitled free claims, arena_shop_buy for cosmetics, pet_show if you already own a pet. Edge cases (first pet free, already-entitled claim, one pet per bot) are spelled out rather than inferred.

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