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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds one genuinely useful behavioral fact — totals are exact sums, not estimates — but says nothing about the time window (no date parameter exists, so presumably all-time), unit conventions, or what happens for an unknown or empty agent_id.

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 short sentences, front-loaded with the core action and output metrics, then a single qualifier about sum accuracy. No redundant restatement of the title and no 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?

An output schema exists, so the description need not explain return values, and the metric list is a helpful preview. However, for a required identifier with zero schema documentation and no stated aggregation window or error behavior, the definition leaves the agent guessing on inputs even though outputs are well covered.

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 single parameter has 0% schema description coverage, so the description must carry the meaning of agent_id and it does not: no indication of identifier format (opaque ID vs. name), where it comes from, or whether it must already exist. This is the main usability gap for the only required input.

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 ('aggregate') and resource ('footprint for an agent') and enumerates the exact metrics returned (J, kWh, gCO2e, cost, mean Landauer efficiency). It does not differentiate itself from siblings such as carbon_receipt or intelligence_bound, which likely report overlapping energy/carbon figures for a narrower scope, so an agent must infer the distinction.

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?

Usage is only implied: 'Aggregate ... totals are exact sums of the ledger entries' hints this is the roll-up view versus per-entry tools like list_entries, but no alternative is named and no when-not condition is given. An agent must guess that this is the correct tool for a whole-agent summary rather than a single work item.

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