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

Goes well beyond the annotations by disclosing the return value ('returns its ID'), the posting identity (under your host name), the default confirmation behavior and that it can be toggled off, the external-reach risk requiring user confirmation, and the auth prerequisite (Cotlet API key with app access). These are exactly the behavioral traits the annotations cannot convey.

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?

Purpose is front-loaded in the first sentence and the rest is dense and useful. The confirmation policy is stated twice ('By default you confirm each call...' and 'confirm with the user before each call'), a mild redundancy that keeps it from a 5.

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 two-parameter mutation tool with no output schema, the description covers purpose, source of the ID, return value, confirmation policy, external reach, and auth requirements. Nothing an agent needs to call it correctly is missing.

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 both parameters (body, conversation_id) are already documented in the schema. The description repeats the list_messages origin for conversation_id but adds no syntax, format, or constraint detail beyond that. Baseline 3 is appropriate.

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 and resource ('Send a message to a camper in an existing conversation') and adds scope details ('Posts a message in an Inbox conversation under your host name'). The reference to list_messages as the source of conversation_id lets an agent distinguish this from the read-side sibling without opening a 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?

Provides clear workflow context ('Start from a conversation_id returned by list_messages') and a conditional confirmation rule ('Reaches other people: confirm with the user before each call'). It does not, however, name an explicit alternative or state when not to use this tool, so it stops short of full routing guidance.

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