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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context beyond annotations: it explicitly states 'Takes no arguments — it always describes the calling key, never another account' and 'This is the only tool that never consumes quota,' two non-obvious behavioral traits an agent would otherwise not know. This is a strong addition; a 5 would require even richer detail on output structure or rate-limit nuances.

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?

Three sentences, each earning its place: the first states the report contents and scope, the second gives concrete usage triggers, the third adds the unique no-quota-consumption trait. No filler, no repetition of schema information, front-loaded with purpose.

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?

The output schema exists, so return-value details are handled structurally. The description covers what the tool reports (plan, usage, quota, resets, limits, overage), when to call it, its zero-argument nature, and its unique non-consuming property. For a 0-parameter read-only tool with strong annotations, this is complete.

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?

There are 0 parameters, so the description's job is to confirm the no-argument contract, which it does explicitly ('Takes no arguments'). The baseline for 0 params is 4, and the description earns the extra point by explicitly stating the no-arguments contract and clarifying that it always operates on the calling key, removing ambiguity about what 'no arguments' might default to.

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?

The description uses a specific verb ('Report') with a clear resource ('the plan, monthly and daily call usage, remaining quota, reset times, rate limit and overage status') and explicitly scopes it to 'the DoorProfit API key authenticating this session,' distinguishing it from any other-account tool. It clearly differentiates from siblings like get_crime_data and get_neighborhood_data, which handle different domains entirely.

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?

Provides explicit when-to-use guidance: 'Call it when the user asks how many calls they have left, or after any other tool returns QUOTA_EXCEEDED or DAILY_LIMIT_EXCEEDED.' It also adds a concrete workflow suggestion ('before suggesting an upgrade'), giving the agent actionable context beyond the schema.

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