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

Annotations only provide false hints, so the description carries the behavioral burden. It discloses a consequential trait: the rule is injected only on every NEW chat, not existing chats. It also provides useful limits (15000 chars, max 20 rules per user), though it does not describe edge-case behavior at those limits.

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 focused sentences with the core behavior stated first, followed by examples and constraints. No filler or redundant content exists.

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 one-parameter creation tool, the description covers purpose, content format, limits, and effect on future chats. An output schema exists, so return-value documentation is not needed. A pointer to update or remove alternatives would make it fully complete.

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 schema only names the 'text' parameter as a string with no description. The description fully compensates by defining text as freeform directives, offering concrete examples, and specifying the max length. This adds substantial meaning beyond the schema.

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 uses the verb 'Add' and the resource 'personal user_rule', and clarifies the effect: injected on every NEW chat. It also distinguishes from sibling tools by signaling creation of a personal rule rather than listing, updating, or removing rules.

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?

It conveys the intended use case—creating a new personal rule with freeform directives—but does not explicitly say when to choose this over update_user_rule or remove_user_rule. No alternative tools are named. Usage is implied rather than explicitly routed.

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