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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, non-destructive), yet the description adds real behavioral detail beyond them: it discloses an internal video sync step, a current-vs-previous period comparison, a same-format baseline against the channel's own history, and that output is exactly one recommendation. The undisclosed cost here is that this is a multi-step, potentially slow operation, which the description does not warn about; 'syncs videos' also sits in mild tension with readOnlyHint, though a cache refresh is plausibly non-mutating and idempotent.

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?

A single dense sentence, but it is front-loaded with the tool's identity and each clause (sync, period comparison, per-video diagnosis, rising/declining detection, single recommendation) adds distinct information. It borders on being a run-on list, though no clause is pure 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?

With an output schema present, the description needn't explain return structure, and it still usefully signals that output is one prioritized recommendation rather than a report dump. What is missing for a genuinely heavy orchestration tool is a note on runtime/cost or side effects of the sync step, which would help an agent decide whether to call it or a cheaper sibling first.

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% and both parameters are documented in the schema, including the default channel fallback and the 14-180 day bound. The description only echoes the comparison-window semantics for `days` ('this and the previous period') and says nothing about channel_id behavior, so it adds little beyond structured fields – 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?

States a specific verb chain and resource: 'End-to-end health check: syncs videos, pulls analytics... diagnoses each video's bottleneck... returns ONE prioritized recommendation.' This is clearly distinguishable from siblings like youtube_get_channel_analytics (raw metrics) and youtube_get_channel_overview (summary), since the description emphasizes diagnosis plus a single actionable recommendation.

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?

The phrase 'End-to-end health check' plus the bottleneck taxonomy gives strong implied context for when to reach for this tool over the narrower analytics siblings. However, it never states when NOT to use it (e.g., for a quick metric pull prefer youtube_get_channel_analytics) nor that it is a heavier multi-step operation, leaving the agent to infer the trade-off.

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

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

The annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so the safety profile is fully covered. The description adds one genuinely useful behavioral detail beyond that: comparisons are aligned by age since publishing rather than by calendar window, so short-lived videos are not penalized. It stops short of disclosing result shape, limits (max 5 IDs, single channel), or what happens when a video is newer than first_days.

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?

One sentence, front-loaded with the resource and the fairness/normalization rule, with zero filler. Nothing in it is redundant with the annotations or schema.

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. However, for a comparison tool spanning 2-5 videos across multiple possible channels, the definition never says what dimensions are compared or that all IDs must belong to one channel, leaving the agent to infer scope from the schema.

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 the schema already documents all three parameters, including first_days and the UC... channel ID format. The description reinforces the meaning of first_days ('its own first N days') but adds nothing for video_ids or channel_id; baseline 3 applies when the schema does the heavy lifting.

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 names a specific verb and resource (compare videos) and states the core mechanic: each video is measured over its own first N days after publishing. It does not say which metrics are compared or how it differs from the neighboring youtube_get_video_analytics, so sibling differentiation is left to the name alone.

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?

There is no explicit statement of when to use this tool versus youtube_get_video_analytics or youtube_get_channel_analytics, and no prerequisites or exclusions. Usage is only inferable from the word 'Compare' and the phrase 'on equal footing', which suggests normalizing across videos of different ages but never says so directly.

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

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

Beyond the annotations, it discloses the behaviors an agent could not otherwise infer: that a browser on the server host opens a Google consent screen, that a human must sign in and choose the channel or Brand Account, and that tokens are encrypted at rest and never returned. This makes clear the call is interactive and requires a user present, which matters greatly for a non-idempotent, open-world tool. Note the "read-only permissions" line refers to the granted Google scopes, not to tool behavior, so it does not genuinely contradict destructiveHint=true — though the pairing could briefly confuse a reader.

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?

Front-loaded with the action and auth method, then the mechanics, then the repeat-use note; each sentence adds something. Slightly long for a no-parameter tool, but no sentence is 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 an interactive OAuth flow, the description covers the essentials: browser requirement, human interaction, token handling, and repeat use; an output schema exists so return values need not be described. It omits failure/cancellation behavior and any indication of whether an already-connected channel is duplicated or skipped, which is the main remaining 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?

With zero parameters, there is nothing for the schema to describe, and the description usefully explains that channel selection happens inside the browser consent screen rather than through arguments. That is a meaningful clarification, though it does not say what happens if no channel is chosen or if the account is already connected.

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 ("Connect a YouTube channel") plus the mechanism (Google sign-in / OAuth 2.0), which cleanly separates it from sibling connect-adjacent tools like youtube_list_channels and youtube_disconnect_channel. It also clarifies that repeat calls add more channels rather than replacing the connection.

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?

"Call again to connect additional channels" gives explicit guidance on repeated invocation, and the browser/consent flow makes the context of use clear. It never names a sibling alternative (e.g., use youtube_list_channels to see what is already connected, or youtube_disconnect_channel to undo), so the routing guidance stops short of explicit alternatives or when-not-to-use.

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

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

Annotations already flag destructiveHint=true, idempotentHint=true, and openWorldHint=true, so the safety profile is covered. The description adds real value by naming exactly what is destroyed: the Google OAuth grant is revoked and the local token is deleted, and it warns that explicit confirmation is mandatory. It leaves minor gaps, such as whether revocation affects other channels sharing the same Google account.

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 tightly constructed sentences with the destructive effect front-loaded and the confirmation constraint second. Every phrase earns its place and nothing is redundant padding.

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 annotations cover idempotency and destructive behavior. The description states both effects of the operation and the confirmation gate, which is sufficient for correct invocation. It could go further on partial-failure behavior or shared-account side effects for a destructive, open-world operation.

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% and the confirm parameter already carries the instruction 'Must be true. Ask the user to confirm before setting it,' which is the key semantic. The description's 'Requires explicit confirmation' reinforces that gate but adds no new information about channel_id or the confirm flow, so the schema is doing the heavy lifting.

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 gives a specific verb pair and resource: 'Revoke CreatorOS's Google access for a channel and delete its local token.' This clearly identifies it as the inverse of youtube_connect_channel and distinguishes it from read-only siblings like youtube_list_channels. It does not explicitly name the sibling it complements, which keeps it just 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 by the inverse relationship to connect_channel and by the stated confirmation requirement, but the description never explicitly says when to prefer this over alternatives or what preconditions exist (e.g., channel must currently be connected). 'Requires explicit confirmation' is an invocation instruction rather than tool-selection guidance.

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

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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is fully covered by structured fields. The description adds one piece of real context beyond that — 'Private', signalling the data is scoped to the caller's own authenticated channel — plus a low-cost summary of what the payload contains. It says nothing about rate limits, quota cost, or empty-data behavior, so it is value-adding but not rich.

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?

A single front-loaded sentence fragment that wastes no words, with the distinguishing qualifier ('Private') placed first and the payload contents listed after. It is efficient, though the colon-list format is clipped enough that it reads as a label rather than an instruction.

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-value explanation is not required, and annotations cover the safety profile; with only two well-documented parameters the definition is close to sufficient. The remaining gap is selection guidance against four sibling analytics/overview tools, which the description does not address at all.

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%: the 'days' parameter already documents the window and that it compares against a previous window of equal length, and 'channel_id' documents the UC... format and the omit-to-use-default behavior. The description adds no syntax, defaults, or edge cases on top of that, 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 description names the resource (channel analytics) and enumerates the concrete outputs: period-over-period totals, daily trend, traffic sources, countries, and subscriber split. That is specific enough for an agent to know what data it yields, but it never distinguishes this tool from likely-overlapping siblings such as youtube_get_channel_overview or youtube_analyze_channel_performance.

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?

There is no when-to-use guidance at all: no statement about when this beats youtube_get_channel_overview, youtube_get_video_analytics, or youtube_analyze_channel_performance, and no prerequisites such as needing a connected channel. The only hint is the word 'Private', which implies an authenticated/owned channel but does not route the agent between alternatives.

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

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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=true, destructiveHint=false, so the safety profile is covered. The description adds nothing beyond that: no statement about the time window of stats, whether data is cached or live, or any rate/quota behavior expected of an external YouTube API read. With an output schema present it needn't describe returns, but it still leaves the agent without behavioral context beyond the 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?

It is a single compact fragment with zero filler, but it is under-specified rather than concise: the missing verb and scope statement would cost only a few words and would materially improve selection. Brevity here comes at the expense of clarity.

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?

With one optional parameter, an output schema and full annotations, structural coverage is good, but the description omits the one thing structure cannot convey: how an 'overview' differs from the three analytics/performance siblings in this toolset. For a read tool sitting in a crowded analytics family, that differentiation gap is a real deficiency.

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% and the sole parameter channel_id already documents the UC... format and the omit-for-default behavior, so the description is not required to compensate. It adds no meaning beyond the schema; 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 description is a bare noun phrase ('Channel profile, public stats, library composition... upload cadence') with no verb and no stated scope such as whose channel is read. The listed content gives a reasonable sense of what data comes back, but it never distinguishes this 'overview' from sibling tools like youtube_get_channel_analytics or youtube_analyze_channel_performance, which plausibly return overlapping metrics.

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?

There is no when-to-use guidance at all: no mention of when to pick this over youtube_get_channel_analytics, youtube_analyze_channel_performance, or youtube_list_channels. The only usage hint in the whole definition lives in the schema ('Omit to use the default connected channel'), not the description.

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

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

Annotations already declare read-only, idempotent, non-destructive, open-world behavior, so the bar is lower. The description does add real scope information beyond annotations: only top-level comments are returned (replies excluded) and extra computed fields (questions, most-liked) are attached. It says nothing about pagination, the 100/300 result cap, or quota behavior.

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?

A single well-formed sentence with the most important qualifier ('top-level') front-loaded and no filler. It is efficient, though arguably under-specified rather than tight.

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. However, for a tool with four parameters and a default result order that materially changes what an agent sees, the description offers no guidance on ordering, limits, or channel scoping, leaving gaps the schema does not fill.

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 75%: order, video_id and channel_id carry descriptions, while max_results only has bounds and a default. The description adds no parameter meaning at all, so it neither compensates for the coverage gap nor clarifies enum/default behavior. Baseline 3 is appropriate given the schema does most of the work.

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?

Names the resource precisely (top-level comments on a video) and scopes it to non-reply comments, plus flags derived signals (questions, most-liked). The retrieval verb is only implied by the tool name rather than stated, and no sibling tool is named, but the resource is unmistakable.

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?

The only usage hint is the trailing phrase 'for audience analysis', which implies intent but never states when to call this versus other video/analytics tools or any prerequisites (e.g. needing a video_id from youtube_list_videos). No exclusions or alternatives are given.

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

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

The annotations already declare that the tool is read-only, idempotent, non-destructive, and open-world, so the safety profile is covered. The description adds useful context that the results are historical records paired with baselines. It does not disclose ordering, whether the history is bounded, or how 'limit' truncates the list, which are behaviors an agent would want to know.

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?

It is a single front-loaded sentence with no filler, and the purpose is stated before the use case. The parenthetical about baselines is efficient. It is slightly terse for a tool that has an undocumented parameter.

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 the description does not need to explain return values, and the annotations cover safety. The remaining gaps are ordering, limit behavior, and channel scoping. For a simple two-parameter read tool, this is adequate but not complete.

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 only 50%: channel_id is documented in the schema, but limit is not documented beyond its numeric bounds. The description adds no meaning to either parameter; it says nothing about what limit counts, what order results come in, or that omitting channel_id falls back to the default connected channel. It therefore fails to compensate for the coverage gap.

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 states a specific verb and resource: retrieving recommendations that were made earlier, together with their baselines. This clearly separates it from the sibling youtube_recommend_publishing_time, which generates new recommendations rather than reading past ones. It does not explicitly name that sibling, but the phrase 'made earlier' makes the distinction clear.

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?

The description implies the purpose of the tool through 'so you can check them against what happened next', which indicates that the tool is meant for retrospective review. However, it does not say when to use it versus alternatives, whether to call it before or after an analytics call, or what it excludes.

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

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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds two genuinely new behavioral facts: the data is 'private' (implying the caller must be authorized for that channel) and that impressions/CTR are only 'if available', warning the agent that some fields may be absent. It says nothing about latency, quota cost, or data freshness, so it earns a solid but not exceptional score.

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?

A single front-loaded sentence that opens with scope ('one video') before listing contents. Every clause names a distinct metric family, so nothing is filler, though the enumeration is dense and would read better split from the availability caveat.

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 the length spent enumerating return values is partly redundant with structured data. The description does cover the authorization-relevant 'private' nature, but with a three-parameter, open-world, authenticated tool it leaves out what happens on missing metrics beyond a parenthetical and any note on how days interacts with retention/CTR data.

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% — video_id, channel_id and the days window (with lifetime default) are all documented in the schema itself. The description adds no syntax or format detail beyond that, so the baseline 3 applies; the 'if available' caveat relates to output, not to parameter usage.

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 names a specific verb (retrieve analytics) and a precise scope ('for one video'), then enumerates the metric families returned (totals, impressions/CTR, traffic sources, retention, search terms). This clearly separates it from channel-level analytics, though it never names youtube_get_channel_analytics or youtube_compare_videos as the alternative scopes.

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 only implied by the phrase 'for one video' — an agent can infer this is the per-video counterpart to channel-level analytics, but there is no explicit statement of when to choose this tool over youtube_get_channel_analytics or youtube_compare_videos, and no prerequisite guidance.

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

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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile needs no restating. The description does add one piece of behavior beyond them — that the response includes stored stat history alongside current metadata — but it says nothing about scope, cost, or what the returned history window covers.

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?

A single sentence with the resource front-loaded and the returned fields parenthesized; no filler and nothing buried mid-clause.

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?

With only two parameters, one required, full schema coverage, an output schema, and rich annotations, the short description is nearly sufficient. The only real gap is overlap ambiguity with the analytics sibling, which matters for tool selection in this crowded namespace.

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 both video_id and the optional channel_id (with its default-channel fallback) are already fully documented inline. The description adds only that the tool targets exactly one video, not batch behavior.

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 the resource (a single video's full metadata) and enumerates the returned fields (title, description, tags, duration, format, stats) plus stored stat history, which clearly separates it from list/search siblings. It does not, however, draw the line against youtube_get_video_analytics, which overlaps with the 'stats' and 'history' it advertises.

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 only implied: fetch details once you have a video_id. There is no explicit when-to-use guidance, no mention of when to prefer youtube_get_video_analytics or youtube_compare_videos, and no stated prerequisites (e.g., a connected channel).

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

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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds one useful behavioral fact — that the result marks which channel is the default — but says nothing about behavior when no channels are connected or about auth/scope requirements for reading connected accounts.

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?

A single sentence with no filler, front-loading the core action and appending the default-channel detail. Nothing is redundant with the title or annotations.

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?

With no parameters, rich annotations and an output schema, the description only needs to convey scope, which it does. The one gap is the empty-state behavior (what comes back when no channel is connected), which an agent may need when routing after a failed lookup.

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?

The tool takes zero parameters, so there is no parameter meaning to convey; baseline for a parameterless schema is 4. The description does not over-promise filtering options that do not exist.

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 states a specific verb (list) and resource (YouTube channels connected to CreatorOS) and adds a distinguishing detail — that the default channel is identified. It is clearly separable from siblings like youtube_connect_channel or youtube_set_default_channel, though it does not name them explicitly.

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 only implied: an agent can infer this is the discovery call to run before set_default or disconnect, but the description never says when to use it or when another sibling is preferable. No prerequisites or exclusions are stated.

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

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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description adds real value by specifying the stats are 'lifetime' and 'public' — distinguishing them from the analytics siblings — but it does not mention caching or the fact that a full sync can be forced, leaving that to the schema.

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?

A single front-loaded sentence with no filler; the resource comes first and the returned data is stated immediately. Nothing in it is redundant with the title.

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?

With annotations, a full output schema, and complete parameter documentation, the description is adequate for calling the tool correctly. It is thin for selection, however: it does not distinguish this list operation from search_videos or explain how public lifetime stats differ from the separate analytics tools.

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% and all six parameters (sort, limit, format, offset, refresh, channel_id) carry their own descriptions, including the cache note on 'refresh' and the default-channel fallback on 'channel_id'. The description adds no parameter-level meaning beyond that, so the baseline of 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?

States a specific verb ('List') and resource ('channel's uploaded videos') plus what is returned ('lifetime public stats (views, likes, comments)'). It is clear what the tool does, but it never contrasts itself with the nearby youtube_search_videos sibling, so an agent must infer the boundary between listing a channel's uploads and searching videos.

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 only implied: listing implies you already know the channel, while filtering/searching would suggest another tool. There is no explicit when-to-use or when-not-to-use guidance, and none of the 14 sibling tools (notably youtube_search_videos and youtube_get_video_analytics) are named as alternatives.

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

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

Annotations already declare this a read-only, idempotent, open-world operation, so the safety bar is low; the description goes further by disclosing the derivation method (relative performance against neighbouring uploads) and that the output carries confidence and sample-size caveats. It stops short of stating rate limits or what happens with sparse history, but the methodological disclosure is genuine added context.

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 with the core capability front-loaded and the caveat trailing. The closing clause about confidence and sample sizes leans on output content that an output schema already exposes, so it earns its place only partially.

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?

With an output schema present, the description needn't enumerate return fields, and it correctly focuses on methodology and trustworthiness signals. What remains thin is the operational prerequisite — how much upload history is needed before a recommendation is meaningful — which an agent would want before calling.

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% and each parameter (format, channel_id, timezone_name) is documented with defaults and examples, so the baseline applies. The description adds nothing parameter-specific — notably it does not reinforce the schema's hint that analyzing Shorts and long-form separately gives better results.

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 — 'recommend the best weekday and time block to publish' — plus the inference basis ('how your past uploads performed relative to neighbouring uploads'). This is clearly distinct from the sibling analytics tools (youtube_get_channel_analytics, youtube_get_video_analytics), which report metrics rather than prescribe a scheduling slot.

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?

The description implies the use case (planning when to publish) and mentions validation, but never explicitly says when to call this versus the analytics siblings, nor what prerequisites apply (e.g. minimum upload history). Usage is inferable from the name and purpose statement rather than stated.

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

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

Annotations already declare readOnly, idempotent and non-destructive, so the safety profile is covered. The description adds one genuinely useful behavior beyond that – no YouTube quota is consumed – but says nothing about result ordering, truncation by limit, or what happens when the query matches nothing.

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?

A single compact sentence with the scoping constraint front-loaded and the useful quota note in parentheses. Nothing is wasted, though the parenthetical could have been spent on something an agent cannot get from schema or annotations, such as ordering.

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?

With an output schema present and annotations covering safety, the description only needs to convey scope and cost, which it does. What is missing — result ordering and behavior at the limit boundary — is minor for a read-only search tool.

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 schema already explains query semantics (titles, tags, descriptions) and the default-channel behavior for channel_id. The description adds no meaning beyond that; limit remains undocumented in the prose, which the schema's min/max only partly compensates for.

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 (search) and resource (connected channel's own video library) plus the match mode (keyword). It implicitly separates itself from youtube_list_videos by being a keyword search rather than an enumeration, but never names that sibling, so an agent must infer the distinction.

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?

The phrase 'connected channel's own video library' signals when this applies (local search over your own content), and 'uses no YouTube quota' hints it is cheap to call. There is no explicit when-to-use versus youtube_list_videos or youtube_get_video_details, and no stated precondition that a channel must already be connected.

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

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

Annotations already declare destructiveHint=true, idempotentHint=false, and openWorldHint=true, so the safety profile is covered. The description adds nothing beyond them: it does not say the previous default is replaced, whether the setting persists across sessions or is per-user/per-workspace, or what confirmation is returned. For a mutation of persistent state, that is a real gap.

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?

One sentence, front-loaded with the verb and zero wasted words. Nothing redundant or padded.

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?

The tool is simple (one required param, output schema present, annotations cover safety), so the short description is close to sufficient. What is missing is the effect on existing state (overwriting the prior default) and the precondition that the channel be connected, both of which matter given destructiveHint=true.

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% and channel_id is documented with its UC... format, so the schema carries the parameter burden. The description does add the semantic link that this parameter becomes the fallback used by other tools, but gives no constraint such as 'must be a connected channel'.

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 action and resource (set the default channel used by tools) in a single unambiguous sentence. It is clearly distinguishable from connect/disconnect/list siblings, though it never names those siblings to reinforce the contrast.

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?

The clause 'when channel_id is omitted' usefully explains when this setting takes effect, implying you call it to avoid passing channel_id on every later call. It gives no explicit when-not guidance, no prerequisites (e.g. the channel must already be connected), and no named alternative such as passing channel_id explicitly instead.

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