epost_store_letter

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

With no annotations, the description carries the full burden and does so well: it discloses that the document is retained (non-destructive), that the target folder is mandatory and enforced by a UI sheet that blocks commit, that indices shift after each store requiring a re-list, and that substring addressing is refused for inboxes over 200 letters. These are non-obvious behavioral and failure-mode facts an agent could not infer from the 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?

Purpose and the critical "not a delete" clarification are front-loaded, and each subsequent sentence adds a distinct operational rule. It is dense and slightly long for a tool description, with the final rationale clause bordering on over-explanation, but no sentence is wasted.

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 4-parameter mutation tool with no annotations and no output schema, the description covers purpose, mandatory inputs, addressing modes, and failure conditions. It stops short of describing what a successful store returns or any authentication/undo context, but nothing essential to invoking 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 coverage is only 50% (index and title are undocumented), and the description compensates: it explains that index addresses the inbox position and is unstable, and that a text substring (the title-style addressing) is matched only against the first 200 letters. folder's required/existing-folder semantics are reinforced; letter_id is left to the schema description.

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?

Names a specific verb and resource ("Archive a letter into a Storage folder"), ties it to the named "Store" action, and explicitly disambiguates from the dangerous look-alike by stating "this is not a delete." An agent can tell this apart from epost_delete_letter without opening either 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 when-to-use context and an explicit exclusion (not a delete), plus practical calling rules (re-list between calls, substring only valid for inboxes of 200 or fewer). It does not, however, contrast with the other filing siblings such as epost_move_to_folder or epost_unfile_from_folder, so the alternative-selection guidance is incomplete.

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