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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description still adds real behavioral value by explaining that a mailbox returns both an 'own' signature and an 'effective' one resolved from mailbox, then campaign agent, then workspace default — a fallback chain that is not inferable from the annotations or parameter schema.

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?

Scope and behavior are front-loaded in the first two sentences, with the alternative-tool guidance following naturally. The trailing documentation URL is somewhat noisy but does not disrupt comprehension; the prose is dense yet free of filler.

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 single-parameter read tool with an output schema (so return shapes need not be explained), the description covers scope, the own-vs-effective resolution order, and the sibling alternative. The only gap is a lack of detail on what happens when a mailbox has no signature at all, which is a minor omission given the output schema.

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 'email' parameter already documents that omitting it targets the workspace default, so the description essentially restates the same rule. Baseline 3 is appropriate; the precedence explanation enriches the meaning of the returned values more than the parameter itself.

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 ('Read the signature') and immediately scopes it two ways: one mailbox when an email is supplied, the workspace default otherwise. It distinguishes itself from the sibling write/preview tools by name, so an agent can tell it apart from argorant_set_inbox_signature or argorant_preview_signature without opening a 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?

It states when to reach for it ('Use it before changing a signature') and routes the adjacent case explicitly to argorant_preview_signature for trying text without saving. The condition that selects between this tool and its closest sibling is spelled out rather than inferred.

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