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

Annotations already declare non-read-only, idempotent, non-destructive, closed-world behavior. The description adds genuine value beyond that by spelling out the side effect of each decision ('allow' lets future emails through, 'reject' blocks, 'cold' marks as cold outreach), which the annotations cannot convey. It does not cover permissions or what happens to already-delivered mail, so it stops short of 5.

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 tight sentences, front-loaded with the action and scope, followed immediately by the value definitions. No filler and nothing redundant with the title.

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 3-parameter, no-output-schema tool, the definition covers the operation and all three decision outcomes adequately. The only gap is the absence of any note about the preconditions of a pending conversation or the tool's effect on the conversation record itself.

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 the baseline is 3, but the description goes further by explaining the semantics of the three enum values rather than just restating the labels. convoId and apiKey remain schema-documented only, which is acceptable given full coverage.

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 (Decide) and resource (screener conversation) with a clarifying parenthetical '(first-time sender)'. It is clearly distinct from neighboring tools like get_convo or mark_convo_read, though it does not explicitly name a sibling to differentiate itself.

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?

The description implies when the tool applies ('a pending screener conversation') and defines each decision value, but it never says when to prefer this over alternatives such as mark_convo_read or update_convo, nor does it state prerequisites like the conversation needing to be in a pending state.

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