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

Annotations already cover readOnly/idempotent/non-destructive, so the bar is lower; the description still adds the auth requirement ('Requires api:read') and notes the response includes app_url as a deep link. It does not discuss pagination or failure modes, but for a static read that is a minor gap.

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 value proposition, then segmented by 'view=' markers that scan cleanly. It is dense and long for a one-parameter tool, with some nested parenthetical detail, but almost every clause conveys distinct information.

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?

With no output schema, the description takes on the return-value burden and does it well, naming the specific fields (tier, display_name, per-feature caps, expires_at, meters, pending_tier_effective_at, prices). An agent can decide and call correctly without further information.

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 0% and the only parameter is an unlabeled enum, so the description carries the full burden — and it does, explaining what each of plan/usage/tiers returns and which is the default. This is meaningfully richer than the bare enum values.

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 ('your Gambit plan, usage and limits') and then enumerates the three distinct data sets the tool returns. No sibling in the list covers billing/plan/limits, so it is unambiguous.

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?

Directly answers the agent's likely query phrasing ('the call for "what's my plan usage"') and maps each view to an intent: plan for current tier/limits, usage for consumed meters, tiers for comparison shopping. It also excludes the mutation case ('changing the plan is done in the app'), though it does not name a sibling alternative explicitly.

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