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

Annotations already declare readOnly, idempotent, and closed-world, so the safety profile is covered. The description adds real value on the output side (shows SSD, date it drops to 0, and potential savings from waiting) and sets a disclaimer boundary. It doesn't contradict annotations.

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?

The core purpose and outputs are front-loaded and dense. The branding sentence ('From Propely (propely.sg), the owner-direct condo marketplace') is promotional filler that doesn't help an agent invoke the tool, costing a point.

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 compensates by enumerating what is returned (SSD amount, zero-date, waiting savings). The purchase/sale date and price inputs are fully covered by the schema, so an agent has enough to call this correctly; only the branding fluff detracts.

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% and all three parameters are self-documented, so the baseline is 3. The description hints that the schedule depends on the purchase date relative to 4 Jul 2025 but adds no syntax or format detail beyond 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?

States a specific verb (calculate) and resource (Seller's Stamp Duty) with a precise scope: selling Singapore residential property within 4 years of purchase. This clearly distinguishes it from siblings like calculate_absd, calculate_bsd, and calculate_seller_net_proceeds without needing to open any 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?

The 'within 4 years of purchase' condition gives a clear triggering context, and the schedule breakdown implies applicability by purchase date. It doesn't explicitly name when to use alternatives (e.g., calculate_bsd for buyer's duty) or state exclusions, so it falls just short of full routing guidance.

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