List instances you have blocked

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

The annotations already communicate readOnlyHint, openWorldHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds no behavioral context beyond that: no mention of pagination behavior, sorting, rate limits, or what exactly is returned. It merely restates the subject matter.

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 extremely short with no wasted words and the core scope is front-loaded. It is a fragment rather than a complete sentence, but given the tool's simplicity, the brevity is mostly appropriate.

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?

The schema and annotations cover parameters and safety, and the title conveys the operation. However, there is no output schema and the description does not explain what the return value looks like (e.g., a list of domain strings) or how pagination works beyond the max_id hint, leaving minor ambiguity for a listing tool.

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 limit, max_id, and account are already fully documented with clear meanings. The description contributes no additional parameter-level nuance, so it sits at the baseline for tools with complete schema coverage.

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 title provides a clear verb+resource: 'List instances you have blocked.' The description reinforces the scope with 'Whole instances,' which distinguishes this from per-account or per-user block tools like get_blocks. However, the description itself is a fragment without an explicit verb and does not name any sibling tool.

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 guidance on when to use this tool versus alternatives such as get_blocks, block_domain, or unblock_domain. The description gives no context about typical use cases, prerequisites, or exclusions, leaving the agent to infer entirely from the name and schema.

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