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

The description discloses that URLs are validated and normalized, that duplicates within the same exclusion are skipped and reported, and that per-URL results are returned. This goes well beyond the sparse annotations (readOnlyHint=false, destructiveHint=false) by describing actual runtime behavior and response shape. It does not claim any irreversible effects, consistent with annotations.

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?

Four sentences, all informative: action, validation/dedupe behavior, return format, and dependency lookups. No filler or repeated schema information; it front-loads the purpose and keeps related references at the end.

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 mutating tool with no output schema and minimal annotations, the description covers the key behaviors an agent needs: what is added, how input is handled, what the response reports, and where to find required identifiers. It could add a note on workspaceId behavior or invalid-exclusionId errors, but the schema and existing pointers largely cover those gaps.

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 coverage is 67%, and the description compensates: it clarifies that profileUrls are validated/normalized and duplicates are handled, and it tells the agent where to obtain exclusionId (get_exclusions). The workspaceId behavior ('required for user keys; workspace keys are bound') is left to the schema, but the description adds enough extra meaning to the required parameters.

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 opens with a precise action: 'Add LinkedIn profile URLs to a manual exclusion entry.' It names the resource (manual exclusion entry) and object (URLs), and distinguishes itself from get_exclusions, list_manual_exclusion_urls, and remove_manual_exclusion_url by its add semantics. This is enough for an agent to select it for append operations.

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?

It explicitly directs the agent to campaignstack_get_exclusions for finding exclusionId values and campaignstack_list_signal_agents for signal agents, covering prerequisite lookups. However, it does not explicitly contrast this with sibling tools like campaignstack_remove_manual_exclusion_url or campaignstack_list_manual_exclusion_urls, so the 'when not to use' guidance is only implied by the name rather than stated.

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