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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so safety is covered. The description adds real context beyond that: exactly what is returned (remaining credits, expiration date, usage history), that complimentary credits are included, and that an API key with app access is required. This is a solid supplement to a safe-read annotation profile.

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 purpose is front-loaded, but the first two sentences are near-duplicates, both restating that credit packages with remaining credits, expiration, and usage are returned. The redundant opening sentence about 'Credit packages of a customer...' wastes space that could carry additional guidance.

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 two-parameter read-only tool with no output schema, the description covers purpose, returned fields, the status filter's meaning, and an auth note, which is close to sufficient. The API-key sentence ('Cotlet API key with access to this app') is slightly vague about the actual credential required, leaving a small gap.

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 100%, so the baseline is 3. The description goes beyond the schema's terse 'active or expired. Default: active' by explaining the practical meaning of status=expired ('packages that have run out'), which adds interpretive value for the one non-obvious parameter.

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 gives a specific verb and resource: it returns credit packages of one customer with credits remaining, expiration dates, and usage history. It distinguishes its content from related tools by noting complimentary credits are included and that the status filter can surface depleted packages. It does not name an alternative sibling, but the scope is clear enough to separate it from get_customer or give_complimentary_credits.

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 provides one concrete usage tip: 'Set status to expired to see packages that have run out,' which clarifies the otherwise ambiguous enum. However, there is no explicit when-to-use-vs-alternatives guidance, e.g. no mention of when to prefer this over get_customer or list_customer_reservations. Usage is implied by the narrow purpose rather than stated.

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