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

Annotations already declare destructiveHint=true and idempotentHint=false, but the description goes well beyond them: releases the number, inbound calls/SMS stop immediately, ~35-day restore_did window before it returns to public stock, pending-order DIDs cancelled with refund, and Bulk Order DIDs cannot be terminated. It also discloses the confirmation-gating behavior.

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?

Front-loads the action, then the alternative, then consequences, then edge cases. Every sentence carries decision-relevant content, though the block is dense and slightly long for a two-parameter tool.

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 annotations covering the safety profile and a 100%-covered schema, the description fills the remaining gaps: recovery window, immediate service impact, refund behavior, and non-terminable cases. Nothing an agent needs to call this correctly is missing.

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 both did_id and confirmation_token are already documented in the schema, including the two-call preview-then-confirm flow. The description adds the 'confirmation-gated' framing but no syntax or format beyond the schema, so 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 and resource ('Terminate (cancel) one of the authenticated customer's DIDs by id') and explicitly distinguishes the action from its softer sibling update_did and its reversal sibling restore_did. An agent can identify exactly what this tool does and how it differs from the surrounding tools.

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?

Explicit when/when-not routing: 'PREFER THE SOFTER ALTERNATIVE FIRST... call update_did with billing_cycles_count: 0 instead' versus 'Only terminate when the user explicitly wants the number gone NOW.' Names the alternative tool, the parameter to use, and the decision condition, leaving nothing to inference.

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