send_contacts_sync

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

Annotations declare readOnlyHint=false but destructiveHint=false, which is ambiguous on its own; the description resolves this by clarifying it 'changes nothing locally' and 'contacts no one else,' and adds the one-way direction and the literal return value. That is real context beyond the structured hints.

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?

Front-loads what the tool does, then trigger, then side-effect profile, then return value, then alternative. Every sentence carries distinct information with no filler.

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?

There is no output schema, but the description states the exact return status ('contacts synced to linked devices'), covers side effects, directionality, and the alternative tool. Nothing needed to invoke it correctly is missing.

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?

Zero parameters, so the baseline is 4. The description reinforces this with 'Takes no parameters,' which is helpful but adds nothing the empty schema does not already imply.

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?

States a specific verb and resource (send contact list as a sync message) plus the direction of flow, 'one-way from this device outward.' It explicitly contrasts with the sibling send_sync_request, so an agent can distinguish it without opening schemas.

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?

Gives a concrete trigger condition ('when contacts added or renamed through signal-mcp do not appear on your phone or desktop') and names the alternative ('to pull data from the primary device instead, use send_sync_request'). This is explicit when-to-use plus alternative routing.

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