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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false), and the description goes well beyond them: it warns that recipientCount is null when NOT COMPUTED and never zero, explains why filtered audiences are null until send time, and states that the tool reads delivery rows only. This is exactly the non-obvious trap an agent needs to avoid misreading a null as zero.

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-loaded with the return payload, then the usage routing, then the recipientCount caveat. The null-semantics explanation runs three sentences and is slightly repetitive, but that nuance is genuinely load-bearing rather than filler.

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?

There is no output schema, so the description must carry return-value semantics itself — and it does, naming the fields and disambiguating the one field whose null is easy to misread. Combined with the sibling routing and prerequisite, an agent has everything needed to call it and interpret the result correctly.

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 schema itself documents both broadcastId and the applicationId default/failure behavior (MCP_APPLICATION_REQUIRED), so the schema does the heavy lifting. The description only restates the list_broadcasts hint for broadcastId and adds nothing about applicationId; its null/recipientCount discussion concerns return values, not parameters. 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?

Opens with a specific verb+resource ('Return full details for a single broadcast') and enumerates exactly what is returned: status, schedule, recurrence rule, linked flow, and delivery breakdown. This clearly separates it from the plural sibling list_broadcasts and the engagement-focused get_broadcast_analytics.

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?

States an explicit prerequisite ('Call list_broadcasts first to find the broadcastId') and an explicit alternative with the condition that selects it ('For per-message-block engagement stats use get_broadcast_analytics instead'). An agent can route between the two tools without guessing.

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