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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds genuinely new behavioral context: public cards need no sign-in while private cards require a linked account with access. It stops short of describing failure behavior (nonexistent ID, private card without access), which keeps it out of 5 territory.

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 tight clauses with the core action front-loaded, then auth constraints, then sibling routing and scope exclusions. No filler sentences and nothing repeated across 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?

An output schema exists, so return values need not be explained, and the description still summarizes the payload. Auth requirements, negative scope and sibling routing are all present for a one-parameter read tool. Only error/edge-case behavior for missing or inaccessible cards is absent.

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 'id' parameter, so the baseline is 3. The description restates that the lookup is by ID and clarifies the object is a stream card, but adds no format, type, or sourcing detail beyond the schema, and there is mild ambiguity about whether the ID is a stream ID or a card ID.

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 and resource ('Read a Synoptic stream card by ID') and enumerates the returned fields (title, description, stream URL). It also distinguishes itself from the two closest siblings, get_stream and get_stream_posts, so an agent can select it 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?

Gives explicit alternatives with their selection condition ('get_stream for more metadata', 'get_stream_posts for posts after signing in') and an explicit negative scope ('Does not fetch arbitrary URLs or articles'). Both when-to-use and when-not-to-use are covered.

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