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

Annotations already establish read-only, idempotent, and non-destructive behavior. The description adds meaningful behavioral detail beyond that: it performs voltage-compatibility checking and transparently reports items that could not be counted due to missing vendor data. This gives the agent an honest picture of what the tool will and won't provide.

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 two sentences with no filler. It front-loads the primary function, enumerates specific outputs, adds the important limitation about unpublished vendor data, and closes with a concrete usage example. 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 tool with no output schema, the description enumerates the return values well: total mass, total steady-state power, per-item data interfaces, voltage-compatibility verdicts, and excluded items. It explains the integration with sibling tools and provides a realistic usage scenario. The parameter schema is complete, so no critical information is missing.

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 already documents both parameters fully, including the bus voltage supply-range check and the items array with id and qty. The description adds value by clarifying that product ids come from other tools and that bus voltage is 'your' power bus voltage, tying the parameters to the intended workflow. This goes slightly beyond the schema's plain definitions.

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 identifies the tool's purpose: building an engineering budget for a component stack. It specifies the inputs (product ids, bus voltage) and outputs (mass, power, data interfaces, voltage verdicts, excluded items), and distinguishes itself from sibling tools by focusing on budget assembly rather than component lookup or matching.

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 clear guidance on when to use the tool: 'assemble and sanity-check a subsystem' with a concrete example (3-4 reaction wheels for ADCS). It also implies the ids come from other tools, which routes the agent to the correct workflow. It does not explicitly list exclusions or name sibling alternatives, but the usage context is clear.

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