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

Annotations only declare readOnlyHint=true; the description supplies the non-obvious behavioral truth — GraphQL exposes no native Subscription type, so the tool silently degrades to a customer-scoped TransactionSearchInput, and it cites the upstream issue. That is exactly the kind of behavior an agent could not derive from structured fields, and it does not contradict the read-only annotation.

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?

Purpose is front-loaded in the first clause, followed by the critical caveat, then the mechanism and the escape hatch. Three dense sentences with little waste, though the TransactionSearchInput detail and the node-field enumeration slightly overlap with the schema.

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 carries the return-value burden and does so — telling the agent the response is nodes of transactions and which fields (status/amount/createdAt) to inspect. It also explains the API limitation that shapes the whole tool, so an agent can call and interpret it without outside knowledge.

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?

Both parameters are fully documented in the schema (100% coverage), so the baseline is 3. The description adds context that the underlying semantics are a TransactionSearchInput scoped to the customer, which reframes what customerId actually returns, but it adds no syntax or format detail beyond that.

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 names a specific verb and resource ('List a customer's recurring / subscription payment activity') and then crucially corrects the mental model: the tool does not return Subscription objects but customer transactions. This distinguishes it from siblings like braintree_search_transactions, which would otherwise appear identical.

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?

It gives a clear when-to-use ('trace recurring charges' by inspecting status/amount/createdAt) and a when-not-to-use ('for full subscription CRUD use the legacy server SDK / REST API'). It does not, however, explicitly route the agent against the nearest sibling, braintree_search_transactions, leaving the reader to infer the boundary.

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