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

The description frames the tool purely as advisory retrieval ("Suggest...", "Carrier lookups are cached for a day"), yet annotations declare readOnlyHint=false and destructiveHint=true. Nothing in the text discloses what could be destroyed, what auth or verification is required, or why a lookup is destructive — the agent would reasonably treat this as a safe read. This is an annotation contradiction.

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 short sentences with the action front-loaded and the caching caveat second. The caching sentence is relevant but hangs without explaining whether a stale result is acceptable or how it affects retries.

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?

An output schema exists, so return values need not be described, but for a tool marked destructive with no parameters the description should still cover preconditions (number verified/claimed), side effects, and how it differs from get_forwarding_instructions. None of that is present.

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?

The tool takes zero parameters, so there is no parameter semantics burden; the schema already makes the empty input explicit. The phrase "the verified personal number" usefully confirms the target is inferred from account state rather than passed in.

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 first sentence gives a specific verb and resource ("suggest forwarding instructions") scoped to a specific object ("the verified personal number") and context ("inbound onboarding"). However, it never distinguishes itself from the very close sibling get_forwarding_instructions, leaving the agent to guess which one returns carrier-specific suggestions.

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?

The only usage cue is the phrase "during inbound onboarding," which hints at timing but states no when-to-use, when-not-to-use, or prerequisite (e.g. whether the number must already be verified/claimed). No alternative is named even though get_forwarding_instructions and get_phone_number_settings are obvious candidates for confusion.

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