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

Annotations already establish readOnly/idempotent/non-destructive behavior, and the description adds real context beyond them: results are limited to the latest period only, and measures like deprivation cannot be ranked cross-nation. It does not cover output format or pagination, but the added scope constraints are genuinely useful.

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?

Two tight sentences with the core scope statement front-loaded, followed by the one edge-case caveat that matters. No filler or 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?

With safe read-only annotations and no output schema, the description covers period, geographic scope, and the cross-nation caveat, which is enough for correct invocation. It omits any note on the limit/order defaults, which is a minor gap for a ranked-list tool.

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 60%, so the schema carries much of the load. The description loosely maps to the 'layer' parameter ('one measure') and the 'scope' categories (UK/nation/English region), but says nothing about limit, order, or place, so it does not fully compensate for the coverage gap.

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 gives a specific verb+resource ('Councils ranked') and pins the scope (UK/nation/English region) and timeframe (latest period), which an agent can distinguish from siblings like compare_places or get_place. It stops short of naming those alternatives explicitly, so it's clear but lacks direct sibling differentiation.

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 implies when the tool applies (ranking one measure, latest period) and adds a meaningful caveat that measures handled differently per nation are ranked within one nation only. However, it never routes the agent between this and compare_places/get_place when multiple councils are involved, leaving usage inference to the caller.

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