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

Annotations already carry readOnlyHint, idempotentHint and destructiveHint=false, so the description doesn't need to restate safety. It does add context the annotations can't supply: the required billing:read scope, the fact that upgrade targets, prices, limits and credits are included, and the caveat that limits stay frozen on a trial until the paid plan starts.

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 most important detail, what the tool returns, comes first, followed by when to call it, and then the trial caveat and the auth requirement. It is dense and most sentences are useful, but the long run of quoted trigger phrases makes it heavier than it strictly needs to be.

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, so the description must describe what comes back; it does so field by field, including the plan-ladder and Agency extra-accounts data. It also covers the auth prerequisite and the trial edge case, leaving nothing an agent needs in order to call this zero-parameter read correctly.

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?

The tool takes no parameters at all, so there is nothing for the description to disambiguate and the baseline is the maximum. The schema is closed (additionalProperties: false), and nothing in the description conflicts with that.

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 enumerates exactly what the response contains: status, tier, cancel-at-period-end, period end, trial end, pause state, seats in use and the account limit. That field list separates it cleanly from near siblings such as get_credits or manage_plan, which an agent might otherwise confuse with it.

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 names the concrete user intents that select this tool ("upgrade", "change plan", "add accounts", "how many accounts") and tells the agent to call it FIRST. It also defers the trial-limit follow-up to manage_plan, so the boundary between the two tools is explicit.

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