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

The readOnlyHint annotation already confirms this is a safe read. The description adds meaningful behavioral context by disclosing that it aggregates multiple resource types (subscriptions, benefit grants, entitlements) in a single call, which helps the agent understand the tool's composite nature. It still does not detail output format or pagination, but the added aggregation info is substantive.

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?

The description is three short, front-loaded sentences that each earn their place: what it fetches, when it is the best answer, and the backing endpoint. There is no wasted language.

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 one-parameter read tool with no output schema, the description gives adequate return-content hints and the endpoint. However, it omits guidance on when to prefer this over polar_get_customer or the by-external-id variant, which is important for selection among several customer-related siblings.

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 single customer_id parameter is fully documented in the schema. The description adds no additional meaning, format, or constraints beyond what the schema already provides, which is the expected baseline for high schema coverage.

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 has a specific verb ('Fetch') and resource ('everything about one customer'), and it enumerates the included data (active subscriptions, granted benefits, entitlements). It distinguishes the tool by scope ('full state') but does not explicitly name the sibling polar_get_customer, which would make it fully unambiguous.

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 an implied usage context in the form of a question ('The best answer to "what does this customer currently have?"'), which is helpful. However, it does not state when not to use this tool or explicitly compare it with sibling alternatives like polar_get_customer or polar_get_customer_state_by_external_id.

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