Microsoft 365 MCP Server

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

Annotations already indicate destructive/write behavior (destructiveHint:true). Description adds that MIME format saves to Sent Items folder and mentions backend delivery process (though with broken 'see here' reference). Does not disclose failure modes, rate limits, or size constraints for attachments.

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?

Length is appropriate for the tool's complexity. The CRITICAL TIP is usefully highlighted with emoji. However, contains dangling reference ('see here') and slightly repetitive structure ('When using JSON... When using MIME...'). Could be more tightly structured.

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?

Covers primary workflows (immediate send vs draft, format options, attachments) and prerequisites (email lookup). Lacks coverage of return values (no output schema exists), error conditions, success indicators, or message size limits expected for an email sending operation.

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 coverage is 67%, providing decent baseline documentation. Description adds context about JSON vs MIME format options for the body parameter and attachment handling behavior. However, completely ignores includeHeaders and excludeResponse parameters, offering no guidance on when to use these boolean flags.

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?

Clear verb ('Send') and resource ('message') with specific format options (JSON/MIME). Partially distinguishes from sibling create-draft-email by mentioning draft creation as an alternative workflow, though fails to differentiate from send-draft-message which sends existing drafts versus this tool which sends new messages.

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?

Strong explicit guidance with the CRITICAL tip mandating use of list-users tool to find recipient addresses rather than guessing. Mentions draft creation as alternative for later sending, implying when NOT to use this tool. Could clarify distinction from send-draft-message for drafts already created.

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