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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description goes beyond them by naming data sources (Environment Agency, planning.data.gov.uk, police.uk) and disclosing the 'unknown' fallback where a borough publishes no data, plus the straight-line-distance caveat and the 'single home can differ' warning.

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 content is dense and largely earns its place because there is no output schema, but it is delivered as one sprawling semicolon-chained sentence. The critical caveats ('unknown', 'a single home can differ') sit at the very end rather than being front-loaded.

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?

With no output schema, the description must enumerate return content, and it does so comprehensively: flood zone, planning constraints, crime/deprivation/tenure, schools and stations, commute times, council tax bands, and the district page. The only gap is any indication of latency, coverage limits, or what happens for a non-London or invalid postcode.

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?

Only one parameter exists and schema coverage is 100%, so the schema fully documents the postcode field with its own example. The description repeats the format hint ('E17 4QH') without adding syntax the schema lacks. Baseline 3 applies when the schema does the heavy lifting.

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 opens with a specific verb and resource ('Open-data facts at one full London postcode'), which is far more informative than the tautological title. Granularity ('one full London postcode') implicitly separates it from the district-level siblings, but no sibling is named explicitly, so an agent must infer the distinction.

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?

There is no when-to-use or when-not statement, and none of the six siblings (find_london_district, get_district_profile, etc.) are referenced as alternatives. The agent gets a data inventory but no routing guidance for choosing this tool over the district or commute tools.

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