tag_message

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

No annotations are provided, so the description carries the behavioral burden. It discloses the non-obvious storage mechanism ('stored as IMAP Keywords headers'), synchronization behavior ('synced to the server'), and timing ('MailMate will pick up the change on next access'). It could also mention edge cases like requiring at least one of add_tags or remove_tags, but the key mutation semantics are well covered.

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?

Three short, purposeful sentences: the core action, the storage/sync behavior, and a helpful sibling pointer. No redundant filler or restatement of the name, and the most important information is front-loaded.

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 three-parameter mutation tool with 100% schema coverage and an output schema, this is nearly complete. It covers the tag format, sync implications, and how to discover valid tags. It omits edge cases such as whether both add_tags and remove_tags can be combined or whether at least one is required, so it is not a perfect 5.

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 schema already documents all three parameters with clear descriptions. The description adds little beyond the schema's parameter details, but it reinforces that tags are synced as IMAP keywords, which matches the add_tags schema note. This is a baseline 3 situation.

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: 'Add or remove tags on a message.' It immediately clarifies the tool's scope and differentiates it from message-retrieval or message-movement siblings. It also points to list_tags for tag definitions, reinforcing its role in the tagging workflow.

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 gives actionable guidance to use list_tags to see defined tags, which helps the agent choose the right sibling when it needs tag names. It does not state explicit exclusions for when not to use this tool, but the sibling purposes are distinct enough that the main usage context is clear.

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