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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is fully covered without the description's help. The description adds value beyond that by disclosing what the computation returns — the break-even month and a 'default alive within 10 years' verdict — which the agent could not infer from the annotations or input schema. It still omits behavior at edge cases (a monthly burn of 0, infinite runway), so not a 5.

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?

Front-loaded with the core computation and packed into a single dense sentence with no filler; the mode distinction appears early enough to orient the agent. It is slightly overstuffed, stacking outputs and a URL into the same sentence rather than separating them.

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 8 parameters fully documented in the schema, no output schema, and annotations covering side effects, the description supplies the missing piece — what the result contains (runway months, break-even month, default-alive flag). A brief note on how modes interact with the optional growth parameters would make it fully 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?

Schema description coverage is 100% and each parameter already carries a mode-tagged explanation plus defaults and bounds, so the schema does the heavy lifting. The description only reiterates the mode split and does not add cross-parameter semantics such as which fields are ignored in burn mode versus pl mode, leaving it at the baseline 3.

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 computation (months of cash runway) with its two input regimes named explicitly ('burn' mode vs 'pl' mode), plus the outputs it produces. This clearly separates it from siblings like burn_multiple or rule_of_40, which measure ratios rather than runway length.

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 tells the agent how to choose between the two modes based on what data it has (net burn vs. revenue + expenses), which is genuine selection guidance. However, it never says when to reach for this tool instead of a sibling such as burn_multiple, nor does it state preconditions or exclusions (e.g., zero burn, negative runway).

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