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

readOnlyHint=true already tells the agent this is a safe, non-mutating read, so the description only needs to add context. It adds the underlying endpoint (GET /customers/{customer_id}/credits) and confirms the return is per-currency balances, but says nothing about pagination, ordering, or how blocks versus balances relate. Useful but not rich behavioral disclosure.

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?

Two short sentences, purpose front-loaded before the endpoint reference, with no filler. The endpoint line is arguably redundant metadata but is compact enough to justify its place for agents that reason about API routes.

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 three-parameter read-only lookup with no output schema, the description tells the agent what is retrieved and at what granularity (per currency), which is enough to call it correctly. Minor gaps remain around result shape and pagination, but the safety profile is already covered by annotations.

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 customer_id, currency, and include_all_blocks are already documented in the schema; baseline is 3. The description's 'by currency' phrase loosely echoes the currency filter but adds no format, default, or interaction detail beyond the schema.

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 (Get), resource (customer's credit balances), and the grouping dimension (by currency), which distinguishes it from the ledger-oriented sibling orb_get_customer_credits_ledger. It does not explicitly name that sibling, so the differentiation is left to inference rather than stated.

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?

There is no when-to-use or when-not-to-use guidance, and no pointer to the nearest alternative (orb_get_customer_credits_ledger) even though the two tools are easy to confuse. The scope phrase 'by currency' implicitly indicates the use case, but nothing in the text tells an agent when to prefer this over the ledger endpoint.

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