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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is fully covered without the description. The only behavioral addition is 'Returns PV and discount factor', which duplicates the existing output schema rather than adding new context such as rounding, sign conventions, or rate constraints.

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?

Four short sentences, front-loaded with the computation and then use cases, inputs, returns, and a cross-reference. The 'Inputs:' sentence is largely redundant against the schema, but nothing is bloated and the ordering is sensible.

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 three-parameter pure calculation with full schema coverage and an output schema, the description covers purpose, domain, inputs, and result shape. An agent has everything needed to invoke it correctly; the sibling pointer to list_bundles is a bonus.

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%, so the schema already documents future_value (EUR), rate (annual percent) and years. The description's 'Inputs: future value, annual rate %, years' restates the same three fields without adding units, bounds, or edge-case meaning. Baseline 3 applies when the schema carries the load.

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 with the actual formula semantics ('present value of a future sum given a discount rate'), which is enough to separate it from adjacent siblings like calculate_future_value or calculate_compound_interest. It does not explicitly name or contrast any sibling, so it lands at clear-but-undifferentiated rather than 5.

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?

Gives concrete domain context ('DCF, NPV, or retirement planning'), which tells an agent when this tool is the right fit. There is no explicit when-not condition and no routing to the inverse tool (calculate_future_value), so it stops short of the 5 tier.

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