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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds that dedup and lowercasing are optional behaviors, which is minor context beyond the schema. It says nothing about matching strictness or how malformed addresses are handled.

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 sentences, front-loaded with the core action and followed by the optional modifiers. No filler, though the second sentence largely echoes schema defaults.

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 read-only extraction tool with full schema coverage and annotations covering safety, the description is sufficient. No output schema exists, but the return (addresses) is self-evident from the purpose, so no major gap remains.

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%, so all three parameters (text, lowercase, deduplicate) are already documented with defaults. The description's mention of optional dedup/lowercase restates rather than extends the schema, so the baseline 3 applies.

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+resource ('Extract all email addresses') and scopes it to a block of free-form text. It is clearly distinguishable from siblings like clean_email_list and verify_email, which operate on lists or single addresses rather than raw text.

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 parenthetical use cases (notes, pasted documents, signatures) imply when the tool is useful, but there is no explicit when-not guidance and no named alternative (e.g. 'for verifying a known address, use verify_email'). Adequate but leaves routing to inference.

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