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

Annotations already declare readOnly, idempotent, closed-world, non-destructive, so the safety profile is covered. The description adds genuinely new behavior: pure arithmetic with no I/O or external calls, results rounded to 2 decimals, other methods' parameters accepted and ignored, and error-on-unknown-method/missing-required behavior. It does not describe output shape, but an output schema exists.

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?

Front-loaded with purpose and routing, then the per-method parameter contract, then error semantics. Dense but mostly earns its place; the repeated restatement of method-dependence ('other parameters are method-dependent, so supply those named...') is somewhat redundant.

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 calculator tool with an output schema and full annotation coverage, the description supplies everything an agent needs: method enumeration, per-method required/optional inputs, standard-conditional requirements, and error behavior. Nothing essential to correct invocation is 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 coverage is 100% so the baseline is 3, but the description adds cross-parameter conditional logic the schema lacks: which parameters each method needs, that fair_value is required for ASC350 and recoverable_amount for IAS36, and that non-selected methods' parameters are ignored. Minor tension between calling fair_value 'optional' for goodwill_impairment and 'required for ASC350' slightly muddies the guidance.

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 specific verb+resource (impairment testing of goodwill and intangibles) and frames it under named accounting standards (ASC 350 / IAS 36). It explicitly distinguishes itself from valuation_goodwill_ppa (initial goodwill/allocation) and points to asset-type siblings for underlying fair values, so an agent can route correctly without opening schemas.

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?

Gives explicit when-to-use ('annual or triggering-event impairment testing') and per-method selection rules (goodwill_impairment vs intangible_impairment). It names the sibling to use instead for initial goodwill/allocation work and for asset fair values, and states the failure conditions (unknown method or missing required parameter errors out) rather than returning a value.

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