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

Annotations already declare readOnlyHint/idempotentHint/non-destructive, so the safety profile is covered. The description adds genuinely non-obvious behavioral meaning: a form from a blocked sender creates nothing and an inbound letter is not treated as a lead, which is information the agent cannot get from the schema or annotations.

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?

A single tightly packed sentence that front-loads the resource ('the addresses this workspace has blocked'). The metaphorical diction ('knocked', 'letter') costs a little precision but the sentence wastes no space.

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 no parameters and no output schema, the description carries the burden of conveying the return contents, and it does name the per-entry fields (why, when, how many times). The remaining gap is that the figurative phrasing leaves return-field naming informal, but an agent has enough to call and interpret it.

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 tool takes zero parameters, so the baseline is 4. The schema is a closed empty object and nothing in the description contradicts that.

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 states a specific verb and resource (listing the addresses the workspace has blocked) and even sketches what each entry contains. It does not explicitly distinguish itself from siblings like block_a_sender or unblock_a_sender, but the read-of-current-blocklist purpose is unambiguous.

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?

Nothing says when to call this rather than block_a_sender or unblock_a_sender, and no prerequisites or exclusions are given. The description explains what a blocked sender means, which hints at context, but it offers no actual usage routing.

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