reply_to_user

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

With no annotations, the description carries the burden and does well: it discloses the write target (replies.jsonl, global or per-project), the delivery latency (~1 second pickup by seashell-ask), and the blocking-caller semantics. It does not say what happens on a stale/invalid message_id or whether the call can fail silently, which is the remaining behavioral gap.

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?

Four sentences, front-loaded with the action, then the trigger condition and the exclusion. Every sentence conveys either what to send, when to send it, or what happens after — 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?

For a 3-parameter tool with no annotations and no output schema, the description supplies the workflow, the timing, and the write destination, which is enough to invoke it correctly. Missing only failure-mode guidance (invalid or already-replied message_id).

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 100%, so a 3 is the floor; the description adds value by explaining that replies land in a global or per-project file, which clarifies why project_path scoping exists and what it affects. It still does not tie message_id directly to the inbox record it must come from, but the schema covers that.

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?

Specific verb+resource ("Post a reply to a user inbox message") that is instantly separable from siblings like read_user_inbox and read_my_replies. The description also identifies the upstream trigger (a message carrying a reply_token) so the agent knows which resource instance this acts on.

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?

States both the positive condition (message had a reply_token, user is blocking) and the negative case (a plain seashell-msg note needs no reply call — answer in chat). It names the sibling tools that produce each case, leaving nothing to inference.

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