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

No annotations are provided, so the description carries the full burden. It discloses the tool is a calculator (no side effects) and lists outputs. However, it does not elaborate on the health status logic or potential edge cases, which is acceptable for a simple tool but leaves minor gaps.

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 brief paragraph of three sentences, front-loaded with the tool's purpose. It contains a minor redundancy ('runwayleft tool' vs tool name) but is otherwise efficient and clear.

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?

For a simple calculation tool with no output schema, the description adequately explains the return values (months, cash-out date, health status). Given the sibling tools, the context is sufficient for an agent to decide when to use this tool.

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?

Input schema has 100% description coverage, so each parameter's purpose is clear from the schema. The description adds 'cash in bank' and 'monthly burn rate' but does not provide new meaning beyond existing parameter descriptions. Baseline score of 3 is appropriate.

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 clearly states the tool calculates months of runway from cash and burn rate, plus cash-out date and health status. It distinguishes from siblings by specifying 'simple flat runway estimate (no growth or churn modeling)', differentiating it from calculate_saas_runway.

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 advises using this tool for simple flat runway estimates and over mental math for accuracy. It implicitly suggests not using it for growth/churn modeling, but does not explicitly list alternatives or when-not-to-use scenarios.

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