reply_message

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

With no annotations supplied, the description carries the full behavioral burden. "Sends immediately" is a genuinely useful disclosure that this is an unguarded write rather than a draft, but nothing states whether the send is irreversible, who receives a reply-all, whether it threads onto the original, or what is returned; for a mutation tool with zero annotation coverage that is a substantial 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?

Two short sentences with no filler, and the immediate-send warning is front-loaded. The efficiency is real, though it shades into under-specification rather than true crispness.

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?

A three-parameter mutation tool with no annotations, no output schema, and no parameter documentation needs far more than two sentences. An agent cannot determine recipient scope, body semantics, or the result of the call from this definition.

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 0% across three parameters, so the description must compensate and does not. It hints at replyAll only obliquely ("or reply-all") and never explains that id is the target message identifier or that comment is the reply body — a non-obvious name that an agent could easily misread.

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 names a specific verb and resource ("Reply ... to a message") and immediately disambiguates the inline variant ("or reply-all"). It does not differentiate from neighboring tools such as forward_message or send_mail, which is the only thing keeping it from a 5.

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?

There is no guidance on when to reply versus forward_message, send_mail, or create_draft, and no instruction on when replyAll should be true versus a direct reply. The parenthetical implies replyAll is an option but leaves the selection criterion entirely to inference.

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