storekit__check_entitlement

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

readOnlyHint already covers the safety profile, but the description adds real behavioral value: the backing subscriptions are Apple SIGNED payloads (JWS) requiring verification and decoding before field reads. That is a non-obvious operational caveat an agent would otherwise miss. It stops short of describing pagination or error/failure behavior.

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 tight sentences, front-loaded with the core question, then the return-shape caveat, then the optional filter. Every sentence earns its place with no filler.

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 usefully characterizes the return value (boolean plus signed subscription payloads that must be decoded). Combined with 100% schema coverage this is nearly complete; minor gaps are failure/error modes and how product_id interacts with the boolean result.

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 100%, so the schema already documents app, product_id, environment, and transaction_id. The description only echoes the product_id narrowing ('Optionally narrow to one product ID') and adds no format or behavioral detail beyond the schema. 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?

States a specific verb and resource framed as answering 'does this customer currently have access?', and clarifies the return shape (boolean plus backing subscriptions). It distinguishes the entitlement question conceptually from siblings like get_subscription_statuses and get_transaction_info, though it never names an alternative explicitly.

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 description conveys implied usage — check access for a customer given any of their transaction IDs — and notes the optional product_id narrowing. It offers no explicit when-to-use vs when-not guidance or routing to sibling tools (e.g., get_subscription_statuses for the fuller subscription picture).

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