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

Beyond the read-only annotations, it discloses three substantive behaviors: phone numbers are never returned (data redaction), it requires the usage scope (authorization prerequisite), and it costs nothing (no credit consumption, relevant given balance-oriented siblings). Ordering ('newest first') and pagination mechanics are also stated, though rate limits or result caps beyond the schema's 100 are not.

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 definition opens with the resource and ordering, then the content breakdown, then operational notes; every clause carries information. The first sentence is dense with a long parenthetical field list, which costs some readability but no sentence is wasted.

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, the description compensates by enumerating returned fields (time, environment, numbers checked, outcome counts, campaign_ref, request_id) and stating what is withheld (phone numbers). Combined with auth scope, cost, ordering and pagination notes, an agent has everything needed to call it 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 100%, so limit and before are already fully documented, including the next_before hint. The description only reinforces the pagination contract and ordering ('newest first'), adding little semantics beyond the schema, which supports the baseline 3.

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 ('the account's recent activity') and enumerates exactly what it contains: UK screening calls with their fields, plus movements on the UK credit, AU wash and dead number balances. That distinguishes it from screen_numbers and check_dead_numbers, though it never names a sibling explicitly.

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?

Usage is implied by the content description (you call it to review recent screening and balance activity), and pagination guidance is given ('Page back by passing next_before as before'). There is no explicit when-to-use/when-not or contrast with alternatives such as get_account, so the agent must infer selection.

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