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

Annotations already carry destructiveHint=true and readOnlyHint=false, so the destructive nature is disclosed. The description adds little beyond repeating 'Delete'. It doesn't mention side effects (e.g., whether existing emails using this sender are affected, whether it's reversible, or if confirmation is needed). With annotations carrying the destructive signal, a 3 is fair—description adds minimal behavioral context.

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?

Single sentence, no fluff, but extremely terse. It's not padded, but it also doesn't earn points for front-loading substantive guidance—there is none to front-load. 3 seems right for a one-liner that could have been slightly richer.

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 one-parameter delete with destructive annotation and output schema, the description is adequate but minimal. It doesn't explain what happens after deletion, any restrictions, or whether the operation is permanent. Given the simplicity, 3 is appropriate—an agent can likely use it correctly, but the description adds the bare minimum.

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?

The schema has 100% description coverage, with id described as 'Sender ID (from list_email_senders)'. That's sufficient. The description itself doesn't add param detail, but schema does the work, so baseline 3-4; the schema's 'from list_email_senders' actually adds provenance, which is good. I'll give 4 for the schema's clear parameter doc.

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 clearly states the action (Delete) and the resource (a sender by ID). It's distinguishable from siblings like update_email_sender or create_email_sender. A bit of context about what 'sender' means (email sender) would push it to 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?

No guidance on when to use this tool vs alternatives. The description doesn't mention that the id comes from list_email_senders (that's in the schema), nor any caveats like whether deletion is permanent or affects templates/logs. No conditions or exclusions.

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