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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is covered structurally. The description adds one genuinely behavioral fact not in the annotations: '(Cost: 1 credit)'. The rest describes return values that the output schema already documents, so it adds modest value beyond 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?

The opening redundantly repeats the tool name twice ('Open Source Licenses: Open Source Licenses is a software license API'), and the phrase 'it returns SPDX identifiers...' duplicates the output schema. The cost note is appropriately placed at the end, but roughly a third of the text 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 single-parameter, read-only lookup tool with a published output schema and full annotation coverage, the description is sufficient to call it correctly. The only missing piece is guidance on accepted identifier formats or what happens for unknown licenses, which is minor at this complexity.

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 100% with a single required 'name' parameter, so baseline is 3. The description adds a small amount of meaning by saying lookup works 'by name or identifier', hinting that an SPDX identifier may be passed in addition to a plain name, which the schema's example ('MIT') does not make explicit.

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?

State a specific verb and resource: 'looks up open source license details by name or identifier', and enumerates the returned fields (SPDX ID, canonical URL, OSI status, legacy IDs, domain applicability). This is clearly more than a restatement of the name, though no sibling differentiation is offered (none of the listed siblings covers licensing, so risk of confusion is low).

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?

No when-to-use or when-not-to-use guidance is given. The description never states that this is for identifying license terms, checking OSI approval, or that a different tool should be used for e.g. SPDX expression parsing or package license scanning. Usage must be inferred entirely 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.