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

Annotations already carry the safety profile (readOnly=true, destructive=true, idempotent=true, openWorld=true), so the bar is lower. The description still adds real context: the closed_target interacts with opening hours, and certain targets require a Business plan, which is authorization information an agent needs before calling.

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 the core action and destination list, then the closed_target behavior, then the prerequisite. No filler is present, though the target enumeration could be structured more scannably.

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?

This is an 8-parameter mutation tool with zero schema description coverage, no output schema, and no per-parameter documentation. The description conveys the primary action but leaves most parameters and the destructive-write consequence unexplained, which is inadequate for a tool of this complexity.

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 8 parameters with no enums. The description partially compensates by explaining the target values and the closed_target/opening-hours relationship, but leaves number vs number_id, target_id, closed_target_id, auto_record, and time_group_id entirely undocumented.

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 and resource ('Points a number at...') and enumerates the exact routing targets, making the effect unambiguous. It does not explicitly contrast itself with siblings like update_forwarding or uk_divert_number, so it falls short of a 5.

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 enumerated targets, which tell the agent what routing destinations are possible, and it notes a Business-plan prerequisite. However, it never says when to choose this tool over routing-adjacent siblings such as update_forwarding or uk_divert_number.

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