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

Annotations already declare destructiveHint=true, idempotentHint=true, and readOnlyHint=false, but the description adds real substance: 'previous values are not kept' spells out what is destroyed, and the uniqueness/case-insensitivity rule explains a concrete failure mode. It doesn't cover auth requirements or confirm whether partial updates are atomic, but the added context is genuinely beyond the annotations.

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?

Four short sentences, front-loaded with the destructive overwrite warning before the rename semantics. The uniqueness/error sentence is the main point of interest and lands last, and the case-insensitivity detail is duplicated in the schema, which costs a small amount of economy.

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?

For a two-parameter mutation with rich annotations and no output schema, the description covers destruction semantics, optionality, and the duplicate-name error path — everything the agent needs to call it correctly. Return-value explanation is unnecessary here.

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 100%, and the schema already documents both parameters, including the 64-character limit and the case-insensitive collision rule. The description's note that name is optional mostly restates the schema's required list, so this is the baseline 3 rather than added value.

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 states a specific verb and resource — 'Rename an existing segment' — and reinforces it with 'Overwrites the given fields.' Sibling tools operate on other resources (brand, tag, prompt), so the agent can distinguish this from create-segment-tool/delete-segment-tool 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?

Usage is only implied: 'existing segment' signals this is a mutation on an already-created object rather than create-segment-tool, but the description never says when to choose this over siblings or states prerequisites. It does add useful edge-case guidance (omitting name leaves the segment unchanged; duplicates error), which pushes it above a bare 2.

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