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

Annotations already declare readOnlyHint=true, idempotentHint=true, and openWorldHint=false, so the safe, side-effect-free profile is covered without the description. The description's only behavioral addition is the existence of two solve directions, which largely restates the mode enum, and it omits how the 'solve backwards' path is actually parameterized.

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?

Two tight sentences that open with a question an agent can pattern-match to a user's query, then state the second capability. The trailing website URL is promotional rather than operational, a minor deduction.

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 nine-parameter, two-mode tool with no output schema, the description leaves important gaps: it claims the tool can solve for present value of 'a target', but no target future-value parameter exists in the schema, and there is no indication of what the result contains or which inputs become optional in each mode.

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 all nine parameters, their units, ranges, and enum meanings; baseline 3 applies. The narrative example usefully anchors the defaults (amount, contribution, years, rate), but adds no syntax or semantics beyond 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?

The description names a concrete verb+resource (future value calculator) and frames it with a worked example ($10,000 plus $200/month over 10 years), then states it can also solve backwards for present value. It does not distinguish itself from nearby siblings such as compound_interest_calculator, savings_goal_calculator, or annuity_calculator, so an agent picking among growth calculators gets no routing help.

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?

There is no explicit when-to-use or when-not-to-use guidance and no named alternative. The example implies 'use this for projection questions', but nothing tells the agent whether this or compound_interest_calculator is the right sibling for a given query, and the two modes are only implied by the framing.

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