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

With no annotations, the description carries the full disclosure burden, and it omits the modeling assumptions that drive the answer: implied withdrawal rate or safe-withdrawal rule, real vs. nominal returns, inflation handling, and whether the result is in today's dollars. It also never says what the call returns (a single dollar figure). For a financial projection this is a meaningful gap, though the input domain hints at a simple deterministic calculator.

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?

One framing sentence followed by a compact args block; the computed quantity is front-loaded and no sentence is filler. Size is well matched to a two-parameter calculator.

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 two-parameter deterministic calculator with no output schema and no annotations, the definition is workable but incomplete: the return value's form and the assumptions behind the projection are unstated. An agent could call it correctly but could not explain or sanity-check the result it gets back.

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% — the schema only repeats parameter titles — so the description must supply all semantics, and it does: both parameters get meaning, units, and numeric bounds (age 40-80; spending in today's dollars, 5,000-1,000,000). The only soft spot is 'all-in', which is left ambiguous about whether taxes and healthcare are included.

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 states a concrete computation: the savings required to retire at a given age with a given annual spend. That is a specific resource and computed quantity, not a restatement of the name. It does not, however, distinguish itself from the sibling retirement_income_from_savings, which is effectively the inverse calculation, so an agent must infer the routing itself.

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 statement of when to use this rather than net_worth_by_age, net_worth_percentile, or retirement_income_from_savings, and no prerequisites or exclusions. The agent only learns what the tool computes, not when to prefer it.

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