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

Annotations already disclose that this is a destructive, non-idempotent, open-world write operation, so the safety profile is covered. The description adds the auth requirement ('Admins only'), which is genuine value beyond the annotations. It does not explain whether updates overwrite existing title/description or support partial updates, but with annotations carrying the behavioral burden, a 3 is appropriate.

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 zero waste. The core purpose is front-loaded and the permission constraint follows immediately, making it easy to scan and parse.

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 simple admin update tool with four fully documented parameters and rich annotations, the description covers the essential purpose and access requirement. The only gap is the already schema-documented lookup step for 'number' and the lack of explicit sibling routing, which are minor given the surrounding structured data.

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%, with all four parameters documented including the note that 'number' comes from list_group_rules. The description mentions 'title or text', which roughly maps to the schema's title/description fields but adds no syntax, format, or optionality details beyond what the schema provides. Baseline 3 is correct.

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 clear verb ('Change') and resource ('title or text of a group rule'), which distinguishes it from add_group_rule, delete_group_rule, and list_group_rules. It does not explicitly name sibling tools, but the verb+resource combination is specific enough for an agent to select it correctly.

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 'Admins only' clause provides a useful prerequisite, and the implied context is editing an existing rule. However, there is no explicit guidance on when to use this vs. add_group_rule (new rule) or list_group_rules (finding the rule number), leaving the agent to infer the correct usage from the verb alone.

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