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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds meaningful context beyond them: the tool never raises a protocol error, it returns a structured {'error': ...} payload with a concrete example, and retries after correction are safe. The 'FREE' cost note and the infinite-runway edge-case behavior are also disclosed.

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 purpose and the FREE marker, then examples, then usage and error behavior. It is somewhat long with two inline JSON snippets, but each snippet demonstrates a distinct output mode (finite vs. infinite runway), so the length is largely earned.

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 3-parameter read-only calculation, the description covers the purpose, the preconditions, the exclusion, the failure mode, and both output branches, even though an output schema already exists. Nothing an agent needs in order to call it correctly is missing.

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 coverage is 100%, so the baseline is 3; the description goes further by showing how the three parameters interact in a worked example (revenue netted against burn producing net_burn_monthly) and by stating what happens when revenue covers burn. That operationalizes monthly_revenue's semantics better than the schema text alone.

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 verb and resource: 'Compute months of cash runway and the projected out-of-cash date.' It also names the sibling it is not for ('Not for per-unit profitability (unit_economics)'), so an agent can disambiguate without opening schemas.

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 when a cash balance and a monthly burn are known' gives the positive precondition, and 'Not for per-unit profitability (unit_economics)' gives the explicit exclusion plus the alternative to route to.

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