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

Annotations already provide readOnlyHint=true and openWorldHint=true. The description adds valuable behavioral context beyond annotations by specifying that the tool returns multiple results (success rate and median outcome per assumption set), which is not apparent from the schema or annotations. It does not contradict the read-only or open-world hints.

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?

A single, well-structured sentence that front-loads the action and output, with zero filler. Every word contributes to the agent's understanding of what the tool does.

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?

Since there is no output schema, the description correctly explains what the tool returns (success rate and median outcome for each source). For a 14-parameter tool with full schema coverage, the description need not enumerate parameters. It is complete enough for an agent to call the tool correctly, though it could have mentioned the default source behavior or the nature of 'success rate'.

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 the baseline is 3. The description does not reference any specific parameters or add meaning beyond what the schema already documents. It does not need to compensate for gaps, so the baseline 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?

The description clearly states the action ('Runs the same plan'), the resource ('several published capital market assumption sets'), and the output ('success rate and median outcome under each'). It distinguishes itself from siblings: run_retirement_projection presumably runs a single plan with one return assumption, while list_return_assumption_sources only lists sources. The comparative focus is explicit.

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 conveys clear context: use this tool to see how outcomes vary across different return forecast sets ('showing how far the answer moves with the return forecast used'). However, it does not explicitly name alternatives or state when not to use it, so it falls short of the top tier of explicit when/when-not guidance.

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