session_pair

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

Annotations already declare this is a non-readonly, non-idempotent, open-world write, so the safety profile is covered. The description adds real workflow context beyond that: the operation yields an 8-character code the user must type on the phone, and history syncs asynchronously minutes later. It does not explain what happens on re-invocation or failure.

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?

One tightly written sentence that front-loads the action, then the immediate result, then the delayed follow-up. No redundant or filler text.

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?

With an output schema present, return values need no elaboration, and annotations carry the mutation/safety profile. The description supplies the essential workflow (code entry, delayed history), leaving only edge cases like already-paired accounts or code expiry unstated.

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 the phone number format and the account alias charset. The description adds no parameter-level meaning beyond that, so the baseline of 3 applies.

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 names a specific verb and resource ('Lie un nouveau compte WhatsApp à ce serveur'), which no sibling shares, and adds the observable outcome (an 8-character code). It never explicitly contrasts itself with the related session_logout or session_status tools, so sibling differentiation is left implicit.

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 action itself (add a new account), and the note that history arrives shortly gives useful context about what follows. However, there is no explicit when-to-use vs. when-not, no prerequisite (e.g., must you be logged out first?), and no alternative named.

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