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

Annotations already declare readOnlyHint=true, so the read-only nature is covered; the description adds useful semantic detail on what is counted as "saved" and how it was offloaded. It does not address the surprising destructiveHint=true flag on what is clearly a reporting operation, nor does it describe return format. With annotations carrying the safety profile, a 3 is appropriate.

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 primary output and followed by the single usage condition. No filler; every clause carries 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 parameters and no output schema, the description compensates by enumerating the three reported metrics, so an agent knows what it gets back. It is complete for the call itself, missing only any note about the anomalous destructive annotation.

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 and schema coverage is 100%, so the baseline is 4. The description usefully clarifies the semantics of the reported values (own tokens saved, credits spent, spend avoided), which is more than the empty schema conveys.

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 names a specific verb (Report) and the precise resource set it produces: agent tokens saved, credits cost, and estimated large-model spend avoided. The parenthetical mechanism (server-side offloading of reads/edits/classification) makes the scope concrete. It does not name a sibling to differentiate from, so it falls short of a 5.

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?

"Use it to show ROI after a session" gives a clear triggering context for the tool. However, it names no alternative (e.g. assist_balance or get_usage) and states no exclusions, so it is a solid context statement rather than explicit when/when-not guidance.

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