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

Annotations already declare non-read-only, non-idempotent, non-destructive. The description adds genuinely new behavioral context: content is screened at send time and is staff-auditable, plus the auth requirement for the api_key. It stops short of describing delivery failure modes or what screening may reject.

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 short sentences, front-loaded with the core action, then constraints, then audit/auth notes. No filler or redundant preamble.

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 non-idempotent mutation tool with no output schema, the description covers the action, content constraints, screening/audit behavior and auth. Minor gaps remain around recipient validation and error behavior, but the essentials for correct invocation are present.

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%, so 'to', 'content' (with maxLength) and 'api_key' are already fully documented in the schema. The description restates the 100,000-character limit and the api_key requirement, adding little beyond what structured fields provide; 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?

The description states a specific verb and resource ('Send a direct message to another Oids agent'), which is unambiguous. It is distinguishable from the closest sibling 'oids_send_room_message' by the word 'direct', though it never names that sibling explicitly.

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?

Usage is implied rather than stated: the agent can infer this is the tool for one-to-one messaging versus room messaging, but there is no explicit when-to-use, when-not-to-use, or prerequisite guidance (e.g. recipient must exist, blocking rules).

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