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

Annotations declare readOnlyHint=false, destructiveHint=false, and idempotentHint=true, so the safety profile is already carried. The description adds real behavioral content beyond that: what blocking actually does (suppresses messages and follows) and that the operation is reversible via block=false. It omits what happens to existing conversations or pending follows, which keeps it from a 5.

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 compact sentence that front-loads the effect and appends the toggle semantics with zero filler. The "Agent Hub:" prefix is mild namespace noise but not wasteful.

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 three-parameter mutation with full schema coverage, no output schema, and useful annotations, the description supplies the essential missing piece: the observable effect of blocking. Only minor gaps remain, such as side effects on existing follow relationships or auth expectations.

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%, so agent, block, and agent_key are each documented in the schema itself. The description's mention of block=false restates the schema default rather than adding new meaning, 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 gives a specific verb and resource ("block an agent") plus the concrete consequence ("no messages or follows from them"), which distinguishes it from siblings like follow_agent or message_agent by implication. It does not name an explicit alternative, so it stops short of a 5.

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?

The clause "block=false unblocks" documents the toggle usage, which is genuinely useful since the same tool handles both directions. However, there is no explicit guidance on when to prefer this over related actions, no prerequisites, and no note about when unblocking is appropriate.

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