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

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false), so the bar is lower, yet the description adds real behavioral context: the 60-day auto-save window, temporary nature, and that committing later materializes add items as real accounts. It does not mention auth/permission requirements, but the lifecycle disclosure is valuable beyond the 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?

Front-loaded purpose, then structured Args/Returns sections and a nested item-shape block. It is long but the length is justified by the genuinely complex nested item contract; the indentation is slightly scattered but no sentence is wasted.

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 output schema, the description responsibly indicates the return shape ({scenario, analysis} or {error}) and compensates for the 0% schema coverage with full parameter documentation. The internal structure of 'analysis' is left unspecified, which is a minor gap but not needed to invoke the tool correctly.

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% and the items parameter is a formless object with additionalProperties=true, so the description carries the entire burden. It fully documents the item dict shapes (add_debt with enumerated account_type values and HELOC/ARM two-phase fields, add_asset, remove) plus name, description, strategy default (highest_rate/avalanche), and extra_monthly, adding substantial meaning absent from the schema.

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 ('Create a what-if scenario and return its projected impact') and clarifies scope with concrete examples of what a scenario bundles (buy a car, take a mortgage). This clearly distinguishes it from siblings like commit_scenario, update_scenario, and list_scenarios without needing their 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?

Provides clear context for when to use it: a hypothetical/what-if bundling of changes that 'auto-saves for 60 days; committing it later turns its add items into real accounts.' This implies the create-vs-commit workflow, though it never explicitly names an alternative tool or states when NOT to use it, so it falls short of full routing guidance.

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