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

Annotations only declare the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=false). The description adds substantial context beyond that: platform reads the keychain, three distinct failure codes (keychain_not_authorized | keychain_expired | keychain_limit_too_low), the post-success state pull_mode = tempo_keychain, who pays gas, and that no further signing is required. This is exactly the behavioral disclosure annotations cannot carry.

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?

Dense and front-loaded: the setup sequence is stated first, then preconditions, then success state, then cancel alternatives. It is long, but nearly every clause carries actionable information; a small amount of parenthetical notation could be tighter, keeping it just under a 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?

For a chained, stateful, auth-dependent subscription operation this is complete: prerequisites, required prior calls, error codes, resulting state, and cleanup paths are all present. An output schema exists, so return values need not be described.

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 0%, so the description must compensate. It does: tx_hash is identified as the authorize tx_hash returned by accessKey.authorize, and subscription_id is the target subscription being activated. It stops short of restating the explicit type/format of each parameter, but the semantic origin of tx_hash is the key value an agent needs.

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 action (confirming the renewal key) on a specific resource (a Tempo subscription running its own renewal key) and distinguishes itself from shop.subscription.get, shop.subscription.cancel, and shop.subscription.preauthorize by name and role. An agent can select it without opening sibling schemas.

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?

Explicit preconditions are given (merchant must run its own renewal key, key must be authorized by the paying wallet, not revoked/expired, limit must cover one period), plus the required setup sequence (shop.subscription.get -> accessKey.authorize -> this call). Alternatives are named for the exit path: shop.subscription.cancel or accessKey.revoke.

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