real_mortgage_rate

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

With no annotations provided, the description carries the full burden of transparency. It discloses cross-sourcing from RBA F-tables and ABS, explains the computation, and details the output fields including the borrower-stance flag. While it doesn't address rate limits or error behaviors, the read-only nature is evident from the 'returns' framing. This adds meaningful context beyond the bare schema.

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 four sentences, each densely informative: purpose, use case, data sources, and output fields. There is no fluff or redundancy. It is front-loaded with the primary action, making it easy to parse. Every sentence earns its place.

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?

Given the tool's simplicity (no parameters, no output schema), the description is complete. It thoroughly covers what the tool does, why to use it, the underlying data sources, and the return values. An agent can confidently invoke it without additional clarification.

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?

The tool has zero parameters, so the baseline is 4 per the rubric. The description doesn't need to explain parameter semantics since there are none, but it does add context about the output structure, which is ancillary. It fully compensates for the absence of parameters.

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 clearly states the tool's function: 'Returns the current real (inflation-adjusted) standard variable mortgage rate' with a specific verb and resource. It distinguishes from siblings like real_cash_rate by explicitly targeting mortgage rates. The methodology (RBA minus ABS CPI) is also specified, leaving no ambiguity.

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 provides a clear use case: 'Single call answers 'are mortgage holders paying a real cost above inflation?''. It effectively conveys when to use this tool, though it doesn't explicitly mention alternatives or when not to use it. This places it above 'implied usage' but below the explicit alternative naming seen in top-tier examples.

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