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

Annotations already declare readOnly/idempotent/non-destructive/non-open-world, so the safety story is covered. The description adds the non-obvious behavioral detail that results are normally served without contacting the billing provider unless refresh=true forces a re-sync — meaningful context beyond the annotations.

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 sentences, return contents first, the optional-parameter behavior second. 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?

There is no output schema, so the description's enumeration of returned fields (plan, status, renewal/end date, trial state) is exactly the compensation needed. With one optional param and full annotation coverage, nothing an agent needs 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 the baseline is 3; the description goes further by tying refresh=true to a concrete situation ('right after a purchase'), adding timing semantics the schema's 'Re-sync from the billing provider before answering' does not convey.

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) and resource (the user's billing status) and enumerates the returned facets: plan, subscription status, renewal/end date, trial state. That scope cleanly separates it from siblings like list_plans (available plans) or get_quota_status (usage limits).

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 trigger for the non-default path: 'use it right after a purchase' to re-read from the provider. It does not discuss alternatives or when not to call it, but for a single-purpose status read the context is clear enough.

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