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

Annotations cover the safety profile (readOnlyHint=true, destructiveHint=false), and the description adds materially more: a 20-credit cost that is only charged when at least 3 of 6 data sources respond, the EU/UK restriction on Meta commercial ads, and the privacy handling of review themes (no author names). It also states the return shape (findings plus a shareable report URL), which no structured field provides.

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 sentences, front-loaded with the scope statement followed by the output/cost contract; the long enumeration is justified because it defines what the bundle actually delivers. Slightly list-heavy but no wasted sentences.

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 multi-source aggregation tool with no output schema, the description discloses scope, cost gating, source limitations, privacy handling, and the returned report URL. It stops short of stating runtime expectations, partial-failure behavior below the 3-source threshold, or whether the report URL expires, which would be the last pieces an agent needs.

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 all six parameters (including brand cap semantics and the client_domain drafting rule) are already documented in the schema. The description only echoes a couple of those constraints (EU/UK Meta ads, no competitor mention in drafts) rather than adding new per-parameter meaning, 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?

The opening clause 'One competitor in one call' names the verb and resource precisely and enumerates the aggregated artifacts (keywords, Meta/Google ads, SERP, reviews, landing page, backlinks, drafts, summary), which cleanly separates it from the granular siblings like competitor_ads_meta and serp_snapshot. An agent can tell this is the orchestrating bundle without opening any schema.

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?

'One competitor in one call' implies this is the single-call alternative to invoking the individual sibling tools, and the credit-gating rule plus 'EU/UK only' constraint set clear expectations. However, it never explicitly says 'use this instead of calling keywords_for_domain + competitor_ads_meta separately' or when a narrow sibling is preferable, so the routing guidance is implied rather than stated.

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