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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is fully covered by structured data. The description adds only the summary-vs-detail distinction, which is modest additional context; it says nothing about return contents (e.g., whether secrets are masked) or pagination.

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 tight sentences with zero filler, and the dual-mode distinction is front-loaded so an agent grasps the behavior immediately.

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 simple one-parameter read tool with rich annotations and no output schema, the description covers the essential behavior. It could note that key secrets are not exposed in the summary, but nothing an agent needs to invoke it correctly is missing.

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% and the single parameter's schema text ("Key ID for detail view. Omit to list all.") already documents its meaning fully. The description merely restates that same instruction, adding no syntax, format, or edge-case detail beyond the schema.

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?

States specific verb (List) and resource (API keys), and clearly distinguishes two modes: summary listing versus single-key detail. It does not differentiate from siblings like key_create or key_delete, but the core operation 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?

"Pass key_id for detail view. Omit to list all." gives a clear conditional for the two modes, which is genuinely useful usage guidance. However, it offers no guidance about when to reach for this tool versus sibling key tools (key_create, key_delete) or other list tools.

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