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

Annotations already declare this as read-only, idempotent, and non-destructive, so the safety profile is covered. The description adds minor context about operating on a 'live provider session,' which implies a prerequisite, but doesn't elaborate on what happens if the session is invalid or whether the preview consumes resources. It meets the baseline but adds limited behavioral detail beyond annotations.

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 description is a single, compact sentence that starts with the action verb and conveys the essence without fluff. Every word contributes to meaning, making it highly efficient and easy to parse.

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 four required parameters, no output schema, and no schema descriptions, the description is severely inadequate. It does not explain what bagId or sessionId refer to, what targetCoverageSeconds or proofSpanSeconds mean, or what the returned 'exact integer funding and coverage' looks like. The tool is complex, and the description fails to provide the necessary context for correct invocation.

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 description coverage is 0%, so the description must explain parameter meanings. It only mentions 'funding and coverage' which vaguely relates to targetCoverageSeconds and proofSpanSeconds but does not explain any of the four required parameters (bagId, sessionId, targetCoverageSeconds, proofSpanSeconds). The agent has no semantic grounding for constructing the call.

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 ('Calculate') and identifies the exact resource: 'exact integer funding and coverage from a live provider session.' It clearly distinguishes itself from sibling tools like storage.provider_funding_session (which implies session management) and storage.provider_quote (which suggests a quote), while 'preview' highlights its non-committal nature.

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?

The description gives no explicit guidance on when to use this tool versus alternatives like storage.provider_quote or storage.provider_funding_session. It implies a prerequisite by saying 'from a live provider session' but fails to explain the workflow or mention any exclusions. This leaves the agent without clear decision criteria.

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