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

Annotations already declare readOnly, idempotent, openWorld=false and non-destructive, so the safety profile is covered. The description goes beyond them with genuinely useful behavior: nearest-cent half-up rounding, the final withdrawal clearing residual balance, and the guarantee that rates are entered rather than fetched.

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 dense sentences, front-loaded with the core computation and then the period/rounding details, with no filler. It is information-rich but slightly packed, which costs a little readability.

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?

With a full output schema, the return values need not be re-explained, and annotations cover safety. The description supplies the calculation convention (level end-of-period, half-up rounding, residue clearing) that an agent needs to invoke it correctly, leaving only sibling-routing guidance missing.

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 four parameters with ranges, enum values and semantics. The description adds only marginal meaning ('monthly, quarterly or annual periods', 'end-of-period withdrawal', 'final withdrawal clears residue') beyond what the schema states, so the baseline 3 is appropriate.

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names a specific resource (retirement drawdown) and precisely enumerates outputs: level end-of-period withdrawal, total withdrawn, and a complete period table from a balance, return and term. It also draws a boundary ('arithmetic on entered numbers only... rates are entered, never fetched') that separates it from rate-fetching or market-data tools among the many calculator siblings.

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 clear domain (level retirement withdrawals) and the input-source note ('rates are entered, never fetched'), which tells the agent this is a pure offline calculator. However, it never states when to prefer this over the closely related loan_schedule or compound_interest_calculator siblings, nor any exclusions or prerequisites.

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