Publish a message to a custom channel

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

Beyond the sparse openWorldHint annotation, it discloses that typed fields win over request_body on conflict, request_body must be stringified JSON, and that channelAccountId, senders, and recipients are de facto required even though the schema only lists custom_channel_id as required. No contradiction with annotations.

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 dense sentences with no filler. Front-loads the core action, then adds mode and requirement guidance; every sentence 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?

For a 14-parameter tool with no output schema, the description captures purpose, mode, body alternatives, requirements, and how to inspect the full schema. However, it does not qualify the required-fields statement by mode and does not describe return behavior, leaving some gaps.

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 descriptions cover all 14 parameters (100%), so baseline is 3. The description adds meaningful semantics: the typed-fields-vs-request_body priority, the mode's schema-inspection purpose, and execute-time required fields. This exceeds schema alone but leaves detailed field semantics to the schema.

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?

Description opens with a specific verb and resource: 'Publish a message over a specified custom channel into HubSpot Conversations' and clearly scopes it to custom-integrated messaging channels syncing external messages. This differentiates it from sibling tools like SendConversationMessage.

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 use-case context ('custom-integrated messaging channels to sync external messages into HubSpot') and operational guidance (typed fields vs request_body, mode='get_request_schema' to inspect schema). Does not explicitly name when-not-to-use alternatives, so not a 5.

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