Set the mailbox signature

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

Annotations already declare readOnlyHint=false, destructiveHint=true, and idempotentHint=true. The description adds useful behavioral context: storage as a message, HTML/text formats, image embedding from the folder, and required capabilities. It does not explicitly state whether an existing signature is overwritten, but the idempotent hint partially covers repeated-call behavior.

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 three sentences, front-loads the core action, then gives usage, alternative, and requirements. Every sentence adds necessary information with no 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?

The description covers what, when, alternative workflows, and prerequisites, and the schema covers all parameters. However, it does not clarify what happens if both html and text are omitted, which is possible given the schema requires only account. This is a minor gap for a low-complexity 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 the baseline is 3. The description mentions 'HTML and/or text' but does not add meaningful per-parameter semantics beyond what the schema already provides (e.g., 'scripts are stripped', 'derived from html when omitted').

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 states a specific action ('Stores the signature as a message') and a precise resource/location ('mailbox folder "mailmcp-signature"'), which clearly distinguishes it from sibling tools like get_signature. It also clarifies the intended trigger ('when the owner pastes or dictates their signature').

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?

Provides explicit when-to-use guidance ('Use it when the owner pastes or dictates their signature') and an explicit alternative workflow for photo/logo signatures (send an email and move it into the folder). It also lists prerequisites: mailbox signature setup and draft capability.

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