inbox_count

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

With no annotations, the description carries the full behavioral burden and does well: it declares the operation read-only, characterizes cost ('cheap'), and discloses non-obvious counting semantics (expired in-flight leases count as unread; parked excluded). It doesn't cover auth requirements or rate limits, but for a read-only counter this is solid disclosure.

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?

Three compact sentences, zero filler, with the return shape front-loaded and the usage rule and edge-case semantics trailing. Every clause earns its place.

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?

Output schema exists, so return values need not be re-explained; the description supplies the selection context and the subtle counting rules an agent needs to interpret the numbers correctly. Complete for a single-param read tool.

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% and the single agent_id parameter is fully documented in the schema (global inbox, reaches you in any workspace, REQUIRED). The description adds nothing about the parameter, so the baseline 3 applies.

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 (Return) and resource (inbox lane sizes) and enumerates the exact returned fields {unread, in_flight, read}. An agent can distinguish this counting tool from inbox_pull/inbox_peek/inbox_history without opening any schema.

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 explicit usage context ('Cheap READ-ONLY between-turns check') and a routing rule ('pull when unread > 0') that points to the sibling inbox_pull. No when-not-to-use guidance is given, but the positive selection rule is clear.

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