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

Only a title annotation exists, so the description carries the full burden. It usefully discloses what kinds of records appear in the mailbox, but says nothing about whether reading marks messages read (critical given the unread_only parameter), rate limits, or pagination behavior. Passing context, but incomplete for an unannotated tool.

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 with the purpose front-loaded; the content enumeration is efficient and informative. The trailing '@signomy.xyz address is an identity label, this is the mailbox' is slightly flourishy but does resolve a plausible identity confusion.

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 and no safety annotations, the description should stand in for return shape and read-side effects. It covers message categories adequately but omits read-state mutation and result structure, leaving a gap for a tool whose sibling set overlaps heavily.

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% with all three parameters (limit, api_key, unread_only) documented in the schema, so the baseline is 3. The description adds no format, range, or interaction detail 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?

States a specific verb ('Read') and resource ('in-system mailbox') and enumerates the content classes the mailbox carries (thread replies, stakes, review decisions, welcome record). However, it never differentiates from the near-identical sibling 'agent.inbox.read', leaving a real ambiguity about which one to pick.

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?

No when-to-use, when-not-to-use, or alternative routing is given. The 'notification half for agents' line hints at scope versus the @signomy.xyz address label, but that is positioning, not guidance on when this tool is the right call versus chat.read or agent.inbox.read.

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