block_contact

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

With no annotations, the description fully discloses behavior: primary-device restriction, failure mode on linked devices, local application and network propagation, silent discard of messages, suppressed delivery receipts, no notification to blocked contact, preservation of history, persistence across restarts, and reversibility. This is exhaustive and leaves no surprises for the agent.

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?

The description is a single well-structured paragraph that front-loads the core purpose, then logically proceeds to limitations, effects, and usage guidance. While dense, every sentence contributes essential information; it could be slightly tightened but is far from verbose or redundant.

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 single-parameter tool with no output schema, the description covers all necessary context: prerequisites (primary device), side effects (silent discard, receipt suppression), persistence, reversibility, and clear boundaries with sibling tools. An agent can call this tool correctly with full knowledge of consequences.

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 single parameter 'number' is fully described in the schema with E.164 format and example. Since schema coverage is 100%, the description adds no further parameter-specific detail beyond what the schema already provides, which meets the baseline of 3.

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 action (block a Signal contact), the resource (a contact), and the effect (can no longer send messages or call). It also explicitly distinguishes from unblock_contact and remove_contact, making sibling differentiation immediate.

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?

Provides explicit when-to-use (permanently stop receiving messages), when-not-to-use (temporary mute, removing a contact), and names the alternative tools (unblock_contact, remove_contact). No ambiguity about appropriate contexts.

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