Inxmail MCP

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

No annotations provided, so description carries full burden. It explicitly states 'Read-only' (critical safety info) and discloses return value behavior: 'Returns the blacklist entry with block date if found, or a 'not blacklisted' response if absent.' Could improve by mentioning auth requirements or rate limits, but covers essential behavioral traits well.

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?

Four efficient sentences: purpose, return values, usage guidelines, and read-only declaration. Every sentence earns its place. Information is front-loaded with the core action, followed by returns, then alternatives.

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?

No output schema exists, but description compensates by detailing return values ('blacklist entry with block date' vs 'not blacklisted' response). No annotations exist, but description states read-only status. Given the tool's simplicity (single parameter lookup), the description provides adequate context.

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 has 100% description coverage ('Email address to check'), establishing baseline 3. The description mentions 'specific email' but adds no syntax details, format constraints, or examples beyond what the schema already provides.

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 opens with 'Check if a specific email is on the explicit blacklist' — a specific verb (Check) + resource (blacklist) combination. It distinguishes from siblings by specifying 'explicit blacklist' versus the blocklist checked by sibling get_blocklist_entry, and explicitly contrasts with list_blacklist and check_email_blocked in the usage guidance.

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?

Provides explicit when-to-use guidance: 'Use this for a single-email lookup; use list_blacklist to browse all entries; use check_email_blocked to check both blocklist and blacklist at once.' This clearly maps tools to their specific use cases and alternatives.

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