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

The annotations already declare readOnlyHint=true, and the description aligns by describing a read operation. It adds valuable context beyond annotations, such as the data being normalized, monthly since 1963, and updated monthly, which helps set expectations about the data's nature and freshness.

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 information-dense but not overly long. It front-loads the core return value and interpretation, then provides usage context and update frequency. The two sentences are somewhat long but each adds necessary detail without redundancy.

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?

The description covers the return fields, interpretation, data sources, update frequency, and usage scenarios. While the optional 'days' parameter is not mentioned in the description, it is fully documented in the schema. The tool is simple with one optional param, and the description is sufficiently complete for an agent to select and invoke it 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?

The schema description coverage is 100% for the single optional parameter 'days', which thoroughly explains the history feature and Gold tier requirement. The tool description does not add parameter-level details, but the schema already carries the full burden, so the baseline of 3 is appropriate.

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 returns a 0-100 global real estate affordability score with specific components (price-to-income and rent-to-income) and data sources (FRED and World Bank). It uses a specific verb 'Returns' and distinguishes itself from siblings by describing exactly what it measures.

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 explicitly states when to call the tool: 'Call when the user asks about housing affordability, home prices vs income, rent burden, or housing market valuation, or when timing real estate acquisitions, multifamily underwriting, or rental-demand investment screens.' It does not mention alternatives or when not to use it, but the context is clear.

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