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

The annotations declare readOnlyHint=true, idempotentHint=true, and openWorldHint=false, so safety is covered. The description adds valuable behavioral context: the MAS TDSR limit of 55%, the 70% income counting rule, the stress-test rate default, and the disclaimer that figures are indicative, not legal or financial advice. This goes beyond annotations but does not cover return format or edge cases.

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 description is two sentences: one explaining the calculation and its key rules, and one providing brand and disclaimer context. It is front-loaded with the core purpose and efficiently covers necessary regulatory details. The second sentence about Propely is slightly promotional but still informative.

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 read-only calculation tool with a detailed input schema and no output schema, the description covers the regulatory context, income counting rules, defaults, and a disclaimer. It omits what the output contains (e.g., pass/fail, maximum loan amount, ratio), but given no output schema, some expectation of return values would be helpful. Overall, it is largely complete for an agent to invoke 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 description coverage is 100%, so the schema fully documents all 8 parameters. The description mentions some semantics (variable/rental income at 70%, stress-test default 4%, tenure default 25) which are already in the schema defaults but reinforces their meaning. No additional syntax or format details are provided 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?

The description states a specific verb ('Check') and resource ('a Singapore home loan against the MAS TDSR limit') and adds a second purpose ('find the maximum loan affordable'). This distinguishes it from siblings like calculate_bsd or calculate_absd, which handle different tax/loan calculations.

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 description implies usage through the regulatory context and mentions income counting rules, but does not explicitly state when to use this tool versus alternatives or what the prerequisites are. It does not name any sibling tools or provide exclusions. The context is clear but lacks explicit usage guidance.

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