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

Annotations already declare a safe, idempotent read. The description adds non-obvious behavior: it returns the full phase record with specific fields and provides a not-found fallback, which goes beyond the structured metadata.

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?

Two sentences with no filler: the main action is front-loaded, the return summary earns its place, and the fallback guidance is a single clause.

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 one-parameter read tool with no output schema, the description covers purpose, return contents, and the not-found path. It doesn't specify exact error or empty-result behavior, but this is a minor gap for such a simple operation.

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?

The schema only defines phaseId as a minLength string with no description; the tool description's 'by ID' confirms the parameter's role but doesn't explain where to obtain the phaseId or its expected format. The single, self-explanatory parameter makes this acceptable but not strongly documented.

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 opens with a specific verb and resource: 'Get a campaign phase by ID.' It also lists the returned content (objectives, phase type, order) and the fallback to list_phases, which distinguishes this single-record getter from the enumeration sibling.

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?

It gives an explicit conditional: if not found, use campaignstack_list_phases with a valid campaignId. This is useful routing guidance, though it doesn't spell out broader when-to-use/when-not-to-use alternatives.

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