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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, and the description reinforces with 'Read-only. GET /customers.' It adds value the annotations cannot: exactly what fields come back and an explicit exclusion ('management link and checkout token are never returned'), which tells the agent what data is unavailable downstream.

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?

Front-loaded with the identity of the resource and the 'Plans' alias, then filters, then exclusions and HTTP verb. The middle enumeration of returned fields is dense but each element carries information; only the list is slightly long for a single sentence.

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?

There is no output schema, so the description must carry the return shape, and it does: subscription status, amount and interval, next payment, trial/cancel dates, payment method, coupon, custom fields, and originating form. Pagination semantics live in the schema's offset/next_offset text, so nothing material is missing.

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 baseline is 3. The description earns slightly more by restating the status enum inline and by glossing the date filters as sign-up date range and next-payment date range with worked examples, mapping the schema's 'checkout_from/to' naming onto the user-facing concept.

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 and resource and immediately disambiguates the domain vocabulary ('customers, which the MoonClerk web app calls "Plans"'), then enumerates the per-record contents. This makes it clearly distinguishable from the singular moonclerk_get_customer sibling.

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 concrete usage scenarios ('past_due plans or renewals due this month') and lists the available filter axes, so an agent knows what contexts this fits. It does not explicitly say when to prefer a sibling such as moonclerk_get_customer for a single payer, so it stops short of full routing guidance.

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