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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is partly covered. The description adds meaningful context the annotations cannot express: it is free and no credits are debited, which is exactly the fact an agent needs before deciding to call it.

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 capability and its outputs, then the usage condition, then the free/no-credit note. The trailing example is long but earns its place by making the nested graph shape concrete; nothing else is padding.

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 two-parameter read-only tool with a full output schema, the description covers what it returns at a high level, when to reach for it, and its cost profile. Nothing an agent needs to call it correctly 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?

Schema description coverage is 100%, so both parameters and the whole graph shape are already documented in structured fields. The worked JSON example is a helpful illustration of graph structure, but it mostly restates what the schema already defines, so the 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?

States a specific verb ('Pre-flight-sizes') and resource ('a graph'), and enumerates the concrete outputs: peak memory, engine complexity, tier, credit cost. It also draws the explicit contrast with run_simulation by saying 'without running it', so the agent can tell this apart from its heavier 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?

Gives a clear when: 'when you want to know what a run will cost or how heavy it is before committing', with a qualifier for large or unfamiliar graphs. It does not explicitly name alternatives such as validate_graph or run_simulation, so the routing is implied rather than spelled out.

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