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

No annotations are provided, so the description carries the full burden, and it does so well: it states results are ranked and standardized, that lat/lng is present only 'whenever the reference row carries a coordinate', that UK requests come from Royal Mail PAF, that UK suggestions lack UDPRN/UPRN and require a follow-up validate call, and that the call is billed. These are exactly the non-obvious operational facts an agent needs and none are derivable from the schema.

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 core purpose and the validate_address handoff are front-loaded in the first two sentences, followed by compact parameter notes and a one-line cost disclosure. It is dense but each part earns its place; only the trailing pricing URL sentence runs slightly long for what it conveys.

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 and no annotations, the description still tells the agent what comes back (ranked standardized suggestions with optional coordinates, UK delivery points labelled with building/organisation names), what constraints apply per country, and what follow-up call is needed. Nothing required to call or chain it correctly is missing.

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 0%, so the description has to define all four parameters, and it does: `q` is the partial text typed so far, `country` is ISO-3 and lowercase, `limit` is 1-50 with default 10, and `state` narrows results for USA/Canada. It adds format and range constraints the bare schema lacks.

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 and resource ('Address autocomplete (type-ahead)') plus the returned artifact ('ranked, standardized address suggestions') and the input it operates on ('a partial input `q` typed so far'). That framing is enough to separate it from validate_address, geocode_address, and reverse_geocode without opening 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 concrete use case and a next-step handoff: 'Use it to help a person pick an address, then pass the chosen one to validate_address.' It also conditions behavior by country, including the UK postcode case. It stops short of explicit when-not-to-use guidance, and it describes UK postcode expansion behavior without naming the overlapping sibling expand_uk_postcode, leaving the agent to guess between the two.

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