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

Annotations already declare destructiveHint=true, idempotentHint=true, and readOnlyHint=false, so the safety profile is covered externally. The description adds nothing on top of that: it never says the permission list fully replaces existing permissions, nor mentions rate limits or allowed-sender semantics that are the actual payload. It essentially restates the title.

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 front-loaded sentence with no filler or redundancy. It is efficient, though its brevity reflects under-specification rather than tight editing of rich content.

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-parameter mutation tool with full schema coverage and annotations that carry the destructive/idempotent profile, the definition is minimally sufficient. It still omits any note about the replace-all behavior in prose and offers no guidance on how this interacts with the sibling capability-management tools, so gaps remain.

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 both agent_id and the nested permissions array are already documented, including the critical 'replaces existing' note. The description contributes no additional meaning about capability, rate_limit, or allowed_senders, so the baseline 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 states a specific verb and resource ('update which agents can call each of your capabilities'), which is clearer than the bare title and implies an access-control operation. It does not, however, differentiate itself from the nearby sibling update_capabilities, leaving the agent to infer which one edits capability definitions versus call permissions.

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?

There is no statement of when to use this tool versus alternatives such as update_capabilities, grant_mod, or revoke_mod, and no prerequisites or exclusions are given. The only guidance is the implicit framing of the resource in the single sentence.

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