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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds the qualitative shape of the result ('the low-fee portfolio ends materially higher'), which is useful framing but not a precise disclosure of what the output contains. With annotations carrying the behavioral burden, this lands at the minimum-viable level.

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 sentences, front-loaded with the purpose, followed by a compact example that doubles as a usage illustration. No filler. Slightly dense in the example, but every element earns its place.

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?

An output schema exists, so return values need not be described, and the annotations cover the safety profile. The main gap is that the description does not say whether lowFee must be lower than highFee or how fees interact with the gross 'rate', which an agent might need when constructing inputs. Otherwise it is complete for a read-only calculator.

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 field (portfolio, monthly, highFee, lowFee, years, rate, lang) is already documented with defaults and ranges in the schema. The example in the description illustrates typical units and magnitudes, but adds no syntax or constraint detail beyond what the schema states, so the baseline of 3 is correct.

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 and resource: compare the long-term cost of a high vs low management fee on a portfolio with monthly contributions. It is clear enough to distinguish from generic siblings like compound_interest or inflation_check, but it never explicitly contrasts itself with those alternatives, which is what would be needed for a 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?

Usage context is only implied by the example input. There is no statement of when to pick this over compare_investments or compound_interest, and no prerequisites or exclusions. It is adequate to infer intent but the agent gets no routing guidance.

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