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

Annotations already declare the write/destructive/open-world profile, and the description adds genuinely new behavioral facts: a hard rate limit of 3/day, refusal of suppressed and already-contacted recipients, no footer/logo/tracking injection, and dedupe semantics. That is useful operational context beyond the annotation set.

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 dense sentences with zero filler; the core action leads and the constraints (rate limit, refusals) follow immediately. Every clause carries information.

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 7-parameter mutation tool with no output schema, the description covers the essential behavioral envelope (rate limit, refusal rules, sender identity, formatting behavior). A note on what a successful send returns or whether the send is asynchronous would make it fully complete.

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% and the schema itself explains each field in detail, including dedupe_key idempotency and body_text preference. The description only echoes 'plain text preferred' and the dedupe_key concept, so baseline 3 is appropriate.

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?

States a specific verb and resource ('Send a personalized outreach email') along with the sending channel ('from your own address through the outreach pipeline'), which is precise enough to distinguish it from generic siblings like AddMessageTool. It stops short of explicitly naming an alternative tool, so it does not fully meet the 5 bar.

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?

Usage context is implied by 'outreach pipeline' and the refusal conditions tell the agent when a call will be rejected, but there is no explicit when-to-use vs. alternative guidance (e.g., versus AddMessageTool for non-outreach messages). Adequate but clearly gapped.

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