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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds non-obvious behavioral facts beyond that: the response never includes the full card number (a PCI-relevant constraint that shapes what the agent can do with the result), plus the underlying endpoint GET /customers/{customerId}/payment-methods. It does not state behavior for a customer with no methods on file (empty list vs. error), which keeps it below a 5.

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?

Three short sentences, front-loaded with the resource and its contents, then the security caveat, then the use case, then the endpoint. No filler and nothing repeated from the title.

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?

No output schema exists, and the description compensates by enumerating the returned fields, which is the main thing an agent needs to plan around. With a single fully documented parameter and annotations carrying safety, the only real omission — empty-list behavior — is marginal for a read-only lookup.

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?

One parameter with 100% schema description coverage, and that schema description is thorough (Shopify numeric id versus gid:// format, with an example). The tool description adds nothing about the id beyond restating it in the endpoint path, so the schema is doing all the work — baseline 3.

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?

Names a specific verb and resource ('A customer's payment methods on file') and then enumerates exactly which fields come back (type, brand, last digits, expiry, revoked). An agent can distinguish it from awtomic_get_customer and awtomic_get_customer_addresses without opening any schema.

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?

Gives a concrete triggering scenario: 'Use it to spot expired cards before a renewal.' That anchors the call in a real workflow. It stops short of explicit exclusions or naming an alternative tool for the other payment-related cases (e.g. awtomic_send_payment_update_email), so it is clear context without full routing guidance.

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