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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds valuable behavioral context beyond the annotations: the tool is free, and it discloses that external actions require a person's approval. This helps the agent understand the operational implications of the returned permissions.

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?

Two sentences, front-loaded with the core purpose, followed by a compact list of returned fields. The closing 'Free.' is a single-word sentence that earns its place by conveying cost behavior without elaboration. No wasted words.

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 zero-parameter, read-only identity tool, the description fully covers what an agent needs to know: what data is returned and the approval context for external actions. No output schema exists, but the enumerated return fields provide sufficient completeness for correct invocation and interpretation.

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 has zero parameters and schema description coverage is 100%, so there is no parameter burden. The baseline for zero-parameter tools is 4, and the description adds no unnecessary parameter-related noise.

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 opens with a specific verb and resource: 'Returns this key's identity and permissions.' It then enumerates the exact fields returned (scopes, spend cap, remaining allowance, send/reply capacity, per-action limits, suspension state), which clearly differentiates it from siblings like get_usage or get_operation that focus on operation or usage details.

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 description implies this tool is useful for checking permissions and limits before taking external actions, especially with the note that 'Every external action... needs a person's approval.' However, it never explicitly states when to use this tool versus alternatives or mentions any exclusions, leaving usage guidance to inference.

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