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

Annotations already declare this a read-only, idempotent, closed-world computation, so the safety profile is covered. The description adds genuine context beyond that: the output is explicitly labelled an estimate and the rent figure is caller-supplied rather than fetched. It does not disclose how gross vs net are computed or whether the estimate label reflects any rounding or assumption caveats.

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 with the critical word ESTIMATE emphasized first, and the parenthetical of optional costs is compact rather than repetitive. Slight density from the capitalization and nested parentheses, but no sentence is wasted.

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 no output schema, the description correctly names what comes back (gross and net yield) and flags the estimate caveat, which is the main thing an agent must relay to a user. For a five-parameter pure computation tool whose schema is fully documented, the remaining gap—no worked formula or statement of units on the returned percentages—is minor.

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 all five parameters including the includePurchaseCosts flag are already documented in the schema. The description restates the price, rent, service charge and other-cost inputs but adds no meaning beyond the schema, and notably omits any explanation of the non-obvious includePurchaseCosts default (DLD 4% + admin + trustee) that materially changes the net yield.

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 verb (estimate) and a specific resource (gross and net rental yield), and states the inputs that produce it (price, annual rent, optional costs). An agent can tell this is a yield calculator rather than a search or cost-calculation tool, though it never names which sibling to prefer when the agent also has calculate_purchase_costs or calculate_dld_buying_costs available.

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?

The clause 'MRK does not supply the rent figure' establishes a real precondition: the caller must already have a rent figure, which implicitly routes agents to search_listings when they don't. There is no explicit when-to-use or when-not-to-use statement, and no mention of when the optional cost parameters should be supplied.

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