set_pin

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

With no annotations, the description fully covers behavioral aspects: PIN used for encryption key derivation, 7-day lockout if forgotten. Could mention if changing PIN is possible, but adequate.

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?

Concise yet comprehensive: front-loaded with purpose, then details, usage, alternatives, and warning. No unnecessary sentences.

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?

All relevant context is provided: when to use, consequences, PIN format, alternative tool, warning. No output schema needed given the tool's simplicity.

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 describes PIN as 4-20 digit string; description adds that it derives encryption key and causes lockout if forgotten, enriching the parameter's significance.

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 clearly states the tool sets a Signal Registration Lock PIN to protect against SIM-swap attacks. It distinguishes from sibling tools like remove_pin.

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?

Explicitly says 'Use when you want to harden your account against SIM-swap attacks' and provides alternative remove_pin and a warning about forgetting the PIN.

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