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

The readOnlyHint annotation already declares this is a safe read. The description adds genuinely useful context beyond that, namely that the returned URL is authenticated and requires the secure filename rather than a plain artifact name. It omits expiry/lifetime of the URL and any permission requirements, which would be the natural next detail for a download-URL tool.

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 compact sentences, front-loaded with the purpose, with the parenthetical provenance of the parameter and the REST endpoint appended only after the core statement. No filler.

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 one-parameter, read-only lookup with no output schema, the description covers what the tool returns (an authenticated download URL) and where the input comes from. Only the URL's lifetime/validity is unaddressed, which is a minor gap.

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% for the single parameter, so the schema already documents secureFilename. The description restates that it comes from a build's artifacts list and shows it in the REST path, adding only marginal meaning. Baseline 3 is appropriate.

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+resource+scope: get an authenticated download URL for a build artifact identified by secureFilename, plus the backing REST endpoint. It does not name or contrast with the sibling codemagic_create_artifact_public_url, which is the natural confusion case, so it stops short of a 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?

Usage is implied: the caller must already have a secureFilename sourced from a build's artifacts list. There is no explicit when-to-use versus when-not, and no routing to the public-URL alternative when an unauthenticated link is wanted.

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