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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=false and destructiveHint=false, so the safety profile is covered. The description adds the substantive withholding rules, but says nothing about how limits are sourced, that the result is an estimate, or what form the answer takes.

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?

A single front-loaded sentence that states the computed quantity first and then the two governing rates. Every clause earns its place and nothing is padding.

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 read-only calculator with only one required parameter and full schema coverage, the description supplies the core rule needed to trust the call. The remaining gap is the absence of an output schema combined with no statement of the return value's shape (a dollar amount, possibly plus months withheld).

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 year, annual_earnings, monthly_benefit and the FRA flag in detail; the baseline is 3. The description's rate rules give meaning to why the FRA boolean matters, but that meaning is also already spelled out in 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 specific computation ('How much Social Security withholds under the retirement earnings test') and its inputs (a year and annual earnings), which is clearly distinct from the sibling calculators. It does not explicitly contrast itself with siblings such as get_social_security_limits or calculate_claiming_age_benefit, so it stops short of 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 is implied by the formula it summarizes ($1 per $2 over the limit, $1 per $3 in the FRA year), but there is no explicit statement of when to call this versus the sibling limit or benefit calculators. The agent must infer the selection criteria from the tool names alone.

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