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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), but the description adds real behavioral detail the annotations cannot: exactly one method must be supplied with its declared inputs, no defaults are applied, and invalid input returns an error envelope (INVALID_ARGUMENT) rather than raising. It does not discuss output shape or numeric precision, which keeps it short of a 5.

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?

Purpose and sibling routing are front-loaded, then the method-to-input table follows. The enumeration is long but each entry is load-bearing, since the schema alone does not encode the mapping; there is little fat to trim.

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 no explanation. The description covers method selection, required inputs per method, the exactly-one-method constraint, and error behavior, which is everything an agent needs to invoke a 26-parameter, 11-branch tool correctly.

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% for the 26 individual fields, but the schema cannot express which subset each method requires. The description supplies that complete cross-parameter mapping for all 11 methods plus the one-method-at-a-time rule, which is genuine value beyond the structured fields.

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 opens with a specific verb and resource ('Market-multiple engine') and states the exact scope: apply peer multiples or derive implied multiples for comparable-basis pricing. It explicitly distinguishes itself from calculate_dcf and calculate_residual, so an agent can route correctly without opening the schema.

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?

It gives an explicit when-to-use condition ('market-approach pricing where peers exist') and names two alternatives with the conditions that select them (intrinsic cash-flow value -> calculate_dcf; residual-income/IFRS -> calculate_residual). Nothing is left to inference.

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