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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the safety profile is covered. The description adds that the calculation is monthly and also yields a break-even traffic gain, but says nothing about determinism, rounding, currency handling, or how gross margin changes the result.

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 dense sentence that front-loads the verb, scope, and inputs with no filler. It is arguably over-compressed — the break-even clause is tacked on at the end without structure — but nothing is wasted.

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 closed-form calculator with full schema coverage and safety annotations, the description covers what is computed and roughly what comes back (ROI plus break-even traffic gain). With no output schema, a little more on the shape of the return value and the effect of gross_margin_pct would have completed it.

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 every parameter (including months, currency, gross_margin_pct) is already documented. The description only echoes the required inputs and adds no syntax, unit, or default information beyond the schema, so the baseline of 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 ('Estimates') and a specific resource ('monthly return on an SEO investment'), and enumerates the drivers (visits gain, conversion rate, value per conversion, cost), which distinguishes it from generic ROI/ROAS siblings. It does not name any sibling explicitly, so the differentiation is only implicit.

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?

There is no guidance on when to pick this over campaign_roi, roas_check, break_even, or unit_economics, and no stated preconditions or exclusions. The only implicit cue is the word 'SEO', leaving the agent to infer selection from the tool name.

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