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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds a genuinely useful behavioral fact beyond that: the call deducts from the caller's Geo-IP quota, which is a cost signal the agent can't get from structured fields. It omits rate-limit specifics and failure modes.

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 tight sentences, front-loaded with what is returned, then the cost caveat, then use cases. No filler and nothing buried.

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?

A one-parameter read-only lookup with readOnlyHint/openWorldHint annotations is well covered: the description lists the returned fields (compensating for the absent output schema), states the quota cost, and gives usage contexts. Nothing essential to calling 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?

With a single parameter at 100% schema description coverage, the schema fully documents `ip` including the IPv4/IPv6 format and an example. The description only confirms the accepted address types, adding marginal meaning beyond the schema, so the baseline 3 applies.

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?

States a specific verb (look up) and enumerates the resource returned: geolocation, ISP, organization, country, region, city, coordinates, timezone, ASN for an IPv4/IPv6 address. This is distinguishable from the phone/email/social siblings without opening the 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?

Names concrete use cases (traffic analysis, fraud checks, localizing users), giving the agent a clear context in which to reach for it. It does not, however, name alternatives or exclusions (e.g. when to prefer check_blacklist or check_spam_score instead), so it stops short of full routing guidance.

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