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

Annotations already declare readOnlyHint=false, destructiveHint=false and the open-world/closed-world profile, so the bar is lower. The description adds genuinely useful behavior beyond them: it clarifies the tool persists durable context but performs no sending, and that message_id switches it from create to update mode. It stops short of describing what a save returns or duplicate-handling behavior.

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?

Front-loads the action and scope, then the workflow, then the non-send caveat and the update tip. The 'sponge' metaphor adds flavor at some length, but every sentence carries routing information and nothing is redundant.

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 7-parameter mutation tool with no output schema, the description covers purpose, the downstream workflow, sibling boundaries and the update path well. What is missing is thin: whether the save returns an identifier the agent needs in order to later call send_email with it, which would close the loop on the described workflow.

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 all seven parameters, including the defaults for kind/status/channel and the enum values, are already documented in the schema. The description's only added semantic is the message_id update-vs-create intent, which the schema already states. 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+resource ('Store a generated outreach message on a CRM lead') and enumerates the message kinds it covers (email, LinkedIn, follow-ups). It explicitly distinguishes itself from the send tools in the sibling list with 'Does NOT send anything', so an agent can route correctly 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?

Lays out the full workflow: save here, read back via get_lead_context / list_lead_messages, then push via the channel's own tool (e.g. send_email). It also states the create-vs-update condition ('Pass message_id to update an existing draft instead of creating a new one'), naming the alternative path explicitly.

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