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

No annotations, so description must carry the load. It discloses the verification requirement Link and mentions return of message ID/queue status. Missing rate limits and explicit side effects, but the essential behavior (send, verify sender, queue) is covered.

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?

Two sentences, front-loaded with the essential purpose mud plus the key prerequisite and outcome. No fluff.

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?

Rich schema covers parameter details; description adds the verified-sender requirement and return value (message ID/queue). Could mention rate limits or failure formats, but given the schema's depth, coverage is sufficient for invocation.

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 already documents all 12 parameters with meaningful descriptions (format, max sizes, constraints). The description adds only the 'from' verification linkage, which is also in the schema. At 100% coverage, description adds minimal extra value, so baseline 3.

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+resource: 'Send a transactional email'. The qualifier 'transactional' distinguishes from campaign-send siblings like send_campaign. Mentions the source (verified MisarMail account), tying directly to the 'from' constraint.

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 actionable prerequisite guidance: 'use list_domains to check which sender domains are available'. No explicit when-not-to-use, but the verification check addresses the main failure mode. Could mention alternatives (e.g., template-based sends) but not necessary.

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