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

Annotations already declare this a safe, idempotent, read-only, closed-world operation, so the safety profile is covered. The description adds that output includes a 1-10 score plus 'fixes,' which is useful, but says nothing about result structure, determinism of scoring, or any limits beyond the schema's maxLength.

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?

A single front-loaded sentence that states the action, the output scale, the evaluation criteria, and the remediation in one pass. No filler or redundancy.

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?

With no output schema, the description usefully describes what comes back (score, scored dimensions, suggested fixes), which is the main thing an agent needs. For a one-parameter, no-side-effect tool this is close to sufficient; only the scoring behavior and any input constraints remain unstated.

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?

There is one obvious string parameter ('subject') at 0% schema description coverage, so the description carries the burden of explanation but supplies none. The word 'length' refers to a scoring dimension, not to the parameter's 200-character limit, so no meaning is added beyond the self-evident name.

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 gives a specific verb (score) and resource (a cold email subject line) and enumerates the exact dimensions scored: length, wording that hurts opens, and spam trigger words. This is clearly distinct from every sibling (SPF/DKIM/DMARC/blacklist checks), though it never explicitly names an alternative to distinguish 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?

Usage is only implied: 'cold email subject line' signals the pre-send context, but there is no statement of when to reach for this versus check_cold_email or the other deliverability checks, and no prerequisites or exclusions are given.

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