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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered elsewhere. The description adds real behavioral context beyond that: the default is waiting-messages-only (processed ones excluded unless include_processed), channels covered, and a separate count of still-processing/failed documents.

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-loaded with the core action and payload; three sentences with no filler. The final sentence is a slight restatement of the scoping idea but earns its place by disambiguating against document-search tools.

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 must convey the return shape, and it does: message fields, attachment/processing status, and a processing/failed count. Combined with 5 fully documented optional params, an agent has everything needed to call and interpret it.

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 limit, source, company, unread_only and include_processed are already fully documented, including defaults. The description restates the processed-vs-waiting distinction but adds no format or syntax detail 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 ('Read the company's Incoming inbox') and enumerates the payload (sender, subject, preview, attachments, processing status, plus a processing/failed count). The closing sentence explicitly separates it from document-listing tools: 'Documents alone are not the whole inbox'.

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?

Gives concrete triggers: 'whenever the user asks what is waiting in Incoming, whether anything came in, about an email or message someone sent, or before saying Incoming is clear.' No explicit when-not or named alternative tool, so it stops short of a 5.

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