Inxmail MCP

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

With no annotations provided, the description carries the full burden. It successfully discloses the read-only nature, distinguishes between auto-blocked (hard bounces) and manually blocked entries, and describes the return structure ('summary with blocked status... full entry details'). Minor deduction for not specifying behavior when an email is not blocked.

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 sentences with zero waste: (1) purpose and scope, (2) usage context, (3) return value, (4) preference/safety. Information is front-loaded and every clause earns its place. No redundant or filler text.

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?

For a single-parameter diagnostic tool without output schema, the description is complete. It compensates for missing output schema by detailing return contents, covers safety (read-only) absent annotations, and differentiates from relevant siblings. No significant gaps given the tool's simplicity.

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 100% with the 'email' parameter fully described as 'Email address to check.' The description implies this is the target for block checking but does not add validation rules, format constraints, or examples beyond the schema. Baseline 3 is appropriate given complete schema coverage.

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 a specific verb ('queries') and clearly identifies the dual resources accessed ('blocklist' and 'blacklist'). It explicitly distinguishes this consolidated check from sibling tools 'get_blocklist_entry' and 'get_blacklist_entry' by noting it queries both 'in a single call.'

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 ('first step when investigating why an email isn't being delivered') and clear preference over alternatives ('Prefer this over separate get_blocklist_entry/get_blacklist_entry calls'). This eliminates ambiguity about tool selection order.

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