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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is covered. The description adds two genuinely useful behavioral facts beyond that: the operation costs 2 credits and salary-equivalent calculation requires a paid plan. However, it does not explain what happens with partial or conflicting parameter combinations, which matters for a tool with four optional inputs.

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 substantive content is dense and earns its place, but the leading 'Cost of Living: Cost of Living is a cost of living API' is pure redundancy with the name and title. The credit cost is buried in trailing parentheses rather than surfaced near the capability it applies to.

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?

An output schema exists, so return values need no explanation, and the credit/plan constraints are covered. The remaining gap is mode selection: with zero required parameters, the agent gets no signal about whether to pass `location` alone, `from`+`to`, or `salary`, which is essential to invoking this tool 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?

With 100% schema description coverage, the baseline is 3. The description adds some meaning by noting that states/cities are 'mapped to its Census region', implying regional aggregation, but it never clarifies the relationship between the `location` parameter and the `from`/`to` pair, leaving the agent to guess which mode to use.

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 resource (cost of living index values for US regions) and concrete capabilities (compare relative cost between states/cities, calculate salary equivalents). It is clear, but the opening phrase 'Cost of Living: Cost of Living is a cost of living API' is a tautological restatement, and it never distinguishes itself from siblings like PurchasingPower, CPIInflation, or InflationRate.

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?

Usage is only implied through the phrase 'for relocation decisions', which suggests the appropriate scenario but offers no explicit when-not guidance or named alternatives. An agent must infer that CPIInflation or PurchasingPower are different tools for different questions.

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