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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and a closed world, so safety is covered. The description adds non-obvious behavioral context beyond that: the quota is split into a general call pool and a valuation allowance consumed by specific features, and the 429 failure mode it helps avoid.

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, front-loaded with the return contents and closed with the operational reason to call it. Every clause carries information, including the parenthetical naming which features draw down the allowance.

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 parameters and no output schema, the description carries the full burden and discharges it by describing the returned fields (total calls, valuation allowance breakdown, reset date). An agent knows what it will get and what to do with it.

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 zero parameters, so there is nothing for the schema to document and no semantic gap to fill; the baseline of 4 applies. The description correctly implies the key is inferred from auth rather than passed in.

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 (this key's API usage for the current month) and enumerates exactly what comes back: total calls, the separate valuation allowance broken out by which features draw it down (comps, sold history, trend, flip-score), and the reset date. No sibling tool covers quota/usage, so the differentiation 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?

Gives an explicit, actionable trigger: 'Call it to pace a long run instead of hitting a 429 mid-task.' That is a clear when-to-use condition, though it does not describe when not to bother calling (e.g., short single-call tasks) and there are no alternative tools to route to.

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