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

Annotations cover safety (idempotent, non-destructive, not read-only), and the description adds real context beyond them: 10-minute command expiry, the fact that clear/new_session do not touch the tunnel's MOM memory, vault, or mail, and the constraint to act only in the agent's own conversation. That clarifies the contradiction risk between 'clear' and destructiveHint=false. It does not discuss failure modes or rate limits, so 4 rather than 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?

The core action is front-loaded and no sentence is filler — expiry, scope, and caller restriction each earn their place. The second sentence is dense and parenthetical, slightly hampering readability, which keeps it below a 5.

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 two-optional-parameter mutation tool with full schema coverage and annotations, this is nearly complete: it explains the input round-trip ('they come back in commands') and the answer cycle despite no output schema. Only the concrete response payload shape is left implicit.

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 coverage is 100% and both parameter descriptions are detailed, so the baseline is 3. The prose adds meaning beyond the schema by explaining the owner-visibility consequence of declaring verbs and the intended workflow of receiving commands then answering them. It stops short of documenting response shape (e.g., what 'commands' looks like), hence 4.

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 concrete verbs and resources: start a new session, compact conversation, clear it, plus retrieve and answer pending commands. It is distinguishable from every sibling in the list, which are messaging/vault/storage tools. The 'cable'/'tunnel' terminology is slightly opaque, but the operation itself 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?

It gives a clear cadence: 'Call it whenever you check in,' and a caller constraint: 'Only a cable key of the tunnel uses it.' It also scopes the action to 'your own conversation only.' No explicit alternative tool is named, but none of the siblings overlap, so the missing comparison is low-cost.

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