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

Annotations already mark this as read-only, idempotent, and non-destructive. The description adds behavioral context by specifying the response structure, 404 behavior, and rate limits, which go beyond the annotation flags.

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?

The description is dense but each sentence earns its place: main action, domain context (tactics), usage guidance, error case, rate limits, and return fields. It is longer than minimal but not wasteful.

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?

Given the single-parameter schema, strong annotations, and presence of an output schema, the description is complete: it explains when to use it, what to expect in the response, error handling, and rate limits. No critical gaps remain.

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 input schema covers the single parameter 'defense_id' comprehensively with examples and format hints (100% coverage). The description only references 'slug' indirectly in the 404 sentence, adding no substantial semantic detail beyond what schema already provides.

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 clearly states 'Look up a MITRE D3FEND defense technique' using a specific verb and resource. It distinguishes itself from sibling tools by advising 'Use after d3fend_defense_search for the full record + ATT&CK chain', making the lookup's role distinct.

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?

The description gives explicit sequencing guidance ('Use after d3fend_defense_search') and notes the 404 error on missing slugs, which helps agents decide when to call it. It does not explicitly state when not to use it, but the context is clear enough.

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