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

Far beyond the readOnly/idempotent annotations, it discloses thinness (n_pairs per point, thin_periods), the frequency mismatch (quarterly vs four points in sixteen years), the silent national fallback with the area.index_scope label to check, the 2026-only snapshot nature of rated stock, and non-derivability of RV change on appeal.

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?

Purpose is front-loaded and every paragraph carries distinct information (comparability warning, thinness, fallback behaviour, snapshot caveat). It runs long with heavy capitalization emphasis, but nearly every sentence is load-bearing rather than filler.

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?

For a tool combining three datasets across two incompatible index methodologies, the description covers the caveats an agent needs to interpret results correctly, and the output schema already covers return-shape detail. UK-only and free-to-use scope are stated outright.

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 coverage is 0% and none of the three parameters is described in the schema, so the description must carry the load. It references sector, place and local authority conceptually, but never disambiguates area_key from lad_code, states mutual exclusivity, or gives any expected format.

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 verb+resource bundle: the repeat-sales capital index, the VOA rating-list rent index, and rated stock standing for a sector and place. It is clearly distinguishable from siblings like commercial_index_series and commercial_rent_index_series because it explicitly says it returns all three together.

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?

It gives strong operational guidance — the two indices must never be plotted on one axis, don't quote a move from thin_periods, and only 19 authorities have a capital series so a missing request silently returns the national series. It does not, however, name sibling tools to use when only one index is wanted, so the routing guidance is implicit rather than explicit.

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