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

Annotations declare readOnlyHint=false, destructiveHint=false and openWorldHint=true, so the write-but-non-destructive profile is partly covered. The description genuinely adds context by clarifying that MX records and existing inboxes are untouched and that repeat calls are safe for sender updates. However, the canonicality/idempotency/confirmation boilerplate is generic template text that adds little tool-specific behavior, and the phrase 'no additional confirmation is needed for this read, reversible save...' is muddled for what annotations mark as a write.

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?

The purpose sentence is properly front-loaded, but more than half the text is reusable boilerplate about canonicality, idempotency and confirmation boundaries that is not specific to connecting an email domain. It inflates length without adding callable information.

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 earns points for promising DNS records in the return. It also states the auth prerequisite in general terms. But the prerequisite is self-referential, retry behavior is deferred rather than specified, and there is no mention of what happens on a domain already connected or how it interacts with sibling domain tools.

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 80%, so the schema already explains domain, replyToEmail, senderLocalPart and senderDisplayName well. The description adds no parameter-level meaning beyond that and does not mention the _corply_context object at all, so the baseline 3 is appropriate.

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 opening sentence gives a specific verb and resource ('Connect a company-owned domain for Corply-sent mail') and even states the return artifact (DNS records to publish), which is valuable since there is no output schema. It does not explicitly name siblings like check_email_domain or inspect_email_domain, but the 'does not change MX records or existing inboxes' clause draws a useful boundary against adjacent domain 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?

'Safe to repeat for sender updates' gives one fragment of usage context, but the prerequisite sentence ('plus every prerequisite stated above') is a dangling, vacuous reference to text that does not exist. No alternative is named (inspect_email_domain, check_email_domain, disconnect_email_domain, update_email_sender) and no when-not guidance is provided.

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