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

Adds genuinely non-obvious behavior beyond the readOnly/openWorld annotations: it reads cached competitor data and will never trigger a paid lookup, and keywordsAhead may be null until a competitor is checked. Those are the two facts an agent needs to interpret sparse results correctly. It doesn't say what the ordering or result shape is, but the output schema covers returns.

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?

Three short sentences with the core result front-loaded, then cost behavior, then the null caveat. Every sentence carries information an agent would otherwise have to guess.

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 return shape needn't be explained, and the description still pre-explains the one field an agent would misread (keywordsAhead null). The only real omission is any reference to the projectId argument or to what a competitor entry contains, both partly mitigated by the schema.

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 0% and the description never mentions projectId, so it adds no semantic meaning about the one parameter. The parameter is a self-explanatory UUID named projectId, so the gap is minor, but nothing compensates for the missing schema description.

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 concrete verb+resource: returns competitors plus how many tracked keywords each outranks the user on. This is distinctive enough that an agent can distinguish it from siblings like find_opportunities or get_rank_changes. It stops short of naming an alternative, which keeps it at 4 rather than 5.

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 'uses saved competitor data only' clause implicitly tells the agent when this is the cheap/fast path, but there is no explicit when-to-use or when-to-prefer-another-tool guidance and no sibling is referenced. Usage is inferable rather than stated.

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