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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, yet the description still adds non-obvious behavior: cost of 15 credits (15p), a geographic restriction (UK only), and a conditional output rule (`price_trajectory` appears only with at least two priced snapshots). The empty-result semantics are exactly the kind of context annotations cannot express.

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?

Three short blocks front-loaded with what you get, then output caveats, then cost/region/input workflow. No sentence is filler; each carries a distinct, actionable fact.

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 an output schema present, return values need not be described, yet the description still flags the one conditional output field and the legitimate empty case. Combined with cost, region, and UPRN acquisition path, an agent has everything needed to call this 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 coverage is 0% for the single `uprn` parameter, so the description carries the burden and does so well: it states the tool is keyed on a UPRN rather than an address and routes the agent to `address_autocomplete` and `address_resolve` to obtain one. It omits the accepted numeric format, which is only implied by the schema type.

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 (every marketing snapshot for a property) and enumerates exactly what it contains: asking price over time, price reductions, days listed, status changes, agent, image count, floor plan. That content list distinguishes it from generic siblings like property_history or property_lookup without the agent needing to open any schema.

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 a clear usage context: UK only, keyed on a UPRN not an address, and an explicit two-step prerequisite workflow (`address_autocomplete` then `address_resolve`). It also pre-empts a false-negative interpretation ('no listing at all is a real answer'). It stops short of naming when to prefer a sibling such as property_history or listing_market_series instead.

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