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

Beyond the annotations (destructiveHint=true, idempotentHint=true), the description discloses the actual side effects an agent cannot infer: the variant is deactivated rather than removed, the primary's content is restored, the variant record is retained, and a 409 variants_unavailable error is returned when the workspace lacks the M365 integration. This is exactly the extra behavioral context annotations cannot carry.

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 action and its most important semantic distinction ('reset to primary, not a hard delete'), followed by the failure condition. No filler sentences.

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?

An output schema exists, so return values need no explanation, and the description still covers the mutation's semantics, the retention of the variant record, and the error case. For a 3-parameter mutation tool this is complete enough to invoke correctly.

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 all three required parameters are documented there. The description restates the variant kinds ('reply/internal') but adds no syntax, format, or edge-case detail beyond the schema; the baseline 3 applies when structured fields do the heavy lifting.

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 a precise verb and resource (reset a signature's reply/internal variant to the primary) and immediately clarifies the operation's nature versus what the name implies — explicitly 'not a hard delete'. This lets an agent distinguish it from delete_signature, update_signature_variant, and publish_signature_variant without opening any schema.

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?

Gives clear context for when to call it (the 'reset to primary' action) and names the error condition that blocks it (409 / variants_unavailable without a Microsoft 365 signatures integration). It does not, however, explicitly name the alternative tools (update_signature_variant, delete_signature) or state when-not to use it, so the routing guidance is contextual rather than exhaustive.

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