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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds useful behavioral context: the index is seasonally adjusted with base year 2016, data starts from 1997, and default returns total monthly GDP. This goes beyond annotations and clarifies what the tool returns.

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 concise and front-loaded with the purpose, then provides key data details and parameter guidance. It includes the source and license, which is useful but could be considered slightly verbose. Overall, every sentence contributes to the tool's understanding.

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 purpose, data specifics, default behavior, parameter usage, and data source/licensing. Given that an output schema exists, the absence of return format details is acceptable. The tool is simple with two parameters, and the description fully equips an agent to call 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?

Schema description coverage is 100%, so the baseline is 3. The description adds value by reinforcing the default sector behavior ('Default returns total monthly GDP') and instructing to use the sector parameter for breakdowns. It also provides sector examples that align with the schema, making parameter usage clearer.

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 retrieves UK GDP monthly estimates from the ONS, with specific mention of seasonal adjustment, index base year, and sector coverage. This distinguishes it from other GDP tools (e.g., ABS, BEA, Eurostat) by explicitly naming the UK and the ONS source.

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 for UK GDP data and provides clear guidance on using the sector parameter for breakdowns. It does not explicitly mention alternatives or when not to use, but the scope is clear enough for an agent to select it appropriately among siblings.

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